Fantasy Baseball Waiver Wire: Justin Martinez, Ryan Walker emerge as must-roster closers

We knew the trade deadline would lead to a shift in the bullpen usage of plenty of teams, and that's exactly what we've seen with teams like the Marlins , Angels , and Phillies settling on new closers since the deadline. But those certainly aren't the only closer changes Fantasy players need to know about. In fact, ahead of the Week 21 waiver-wire deadline, we've got three other situations you need to know about that have nothing to do with the trade deadline.

Before we get to the top targets at each position for this week, let's look at three potential new closers around baseball:

1. Justin Martinez , Diamondbacks (25%) – Martinez has two saves in the past week for the Diamondbacks since they announced Paul Sewald would be removed from the ninth inning, and he's even had a couple of other hints that he is, indeed, the closer. In one situation, he was warming behind Sewald, who was starting to run into trouble in the ninth with a four-run lead; he would ultimately get out of the inning without needing to be bailed out, but Martinez was up and ready just in case. In another spot this weekend, he got the win Friday after A.J. Puk failed to hang onto a lead in the eighth inning; Martinez worked a scoreless ninth to put the Diamondbacks in line to walk it off. That sure sounds like a closer.
2. Ryan Walker , Giants (36%) – The Giants didn't just demote the struggling Camilo Doval out of the closer's role this weekend; they sent him back down to Triple-A. Walker was named the closer following Doval's demotion, and though the Giants do have a bunch of potential closers if he falters, Walker has been pretty tremendous in his own right, striking out 71 with just 13 walks in 60.1 innings this season, with a 2.24 ERA. He could be a must-start closer if he hangs on to the job.
3. Lucas Erceg , Royals (14%) –This one is a bit more speculative, but with Hunter Harvey going on the IL, one of Erceg or James McArthur is going to close for the Royals for the time being, and I'm willing to bet on Erceg. He's got the better stuff, and while McArthur was fine as the team's closer, there's a reason they went out and got Erceg even after trading for Harvey. Erceg got the save Saturday, getting four outs across the eighth and ninth to shut the door. That is by no means proof that Erceg is the guy here, but that's who I would bet on if I had to.

Here's who else we're adding ahead of Week 21:

Catchers

Austin Wells , Yankees (42%) – At this point, it feels like Wells probably needs to be viewed as a top-12 option at the catcher position. He's locked in as the Yankees' cleanup hitter behind Aaron Judge and Juan Soto , and has been one of the best catchers in baseball for a while now, hitting .308/.404/.528 since the start of July with 20 RBI. And, with a .384 xwOBA over his past 100 plate appearances, the underlying numbers back it up.

Deep-league target: Adrian Del Castillo , Diamondbacks (8%) – De Castillo didn't come up to the majors with a ton of hype, but he probably should have – after all, the 24-year-old was hitting .319/.403/.608 in Triple-A before his promotion, which is impressive even for the Pacific Coast League. No other qualifying catcher in the PCL had an OPS within even 150 points of Castillo, and he has six hits in his first three MLB games, with at least one RBI in each. With Gabriel Moreno on the IL, I might consider Del Castillo a top-24 catcher already.

First Base

Jake Burger , Marlins (71%) – Burger got off to a rotten start this season, but he's been phenomenal for a while now, hitting .313 with 15 homers, 24 runs, and 26 RBI since July 1. His tendency to swing big might lead to inconsistency moving forward, but we've seen over the past couple of seasons that Burger is a difference maker when he's locked in.

Deep-league target: Jonah Bride , Marlins (7%) – Bride is probably just a Quad-A type player, but it's worth noting that he's been really productive in Triple-A in his career, sporting a .297/.432/.509 line in 166 career games. He's been playing everyday for the Marlins and producing, with three homers, eight RBI, and six runs in 11 games in August. As a deep-league CI option, he might have some appeal as he continues to hit in the heart of the lineup.

Second base

Luis Garcia , Nationals (75%) – The biggest knock against Garcia at this point is that he still isn't an everyday player for the Nationals, as he consistently sits against left-handed pitching. That is, frankly, becoming an indefensible position for the Nationals organization, which owes it to itself to see if Garcia can at least handle lefties; if he can, he might be turning into a legitimate franchise cornerstone. He's hitting .333/.380/.530 with three homers and seven steals since the All-Star break, and even with the platoon playing time gap, he looks like a must-start Fantasy option right now.

Deep-league target: Christian Moore , Angels (4%) – It's usually pretty safe to forget the name of players in their first season after being drafted in redraft leagues, but the Angels are an exception there. They've aggressively promoted several recent first-round picks, and Moore is already crushing the ball at Double-A, with five homers in his first six games. It doesn't really make much sense for them to call him up until they can preserve his rookie eligibility for next season, but that deadline will come next weekend, and I really wouldn't be surprised if we see Moore shortly after that.

Third base

Zach Dezenzo , Astros (13%) – Dezenzo is another prospect who didn't come up with a ton of hype, but maybe he should have, too. He hit .306/.386/.517 in the minors while working his way up to Triple-A, and he's been playing regularly since coming up to the major, too. An 0 for 5 day Sunday against the Red Sox kind of slowed his momentum, but he's still struck out just four times in his first 22 trips to the plate, with solid underlying metrics in his first taste of the majors. And there might be 15-steal upside here, too, so that makes him a name to know in categories leagues.

Deep-league target: Anthony Rendon , Angels (7%) – Get your jokes in, but Rendon has actually looked pretty good since coming back from his latest IL stint, going 7 for 16 with just three strikeouts and even a steal in his first four games back. In deeper OBP leagues, he might still have some appeal.

Shortstop

Zachary Neto , Angels (80%) – Would you believe me if I told you that Neto is a top-50 overall player in Roto leagues this season? Would you believe me if I told you he is a top-10 shortstop in points leagues, too? Well, why would I lie to you? Neto is more widely rostered than we typically try to target for this column, but he's been so outrageously good lately – .338/.441/.634 since the All-Star break – that I'm breaking with tradition to say that Neto is a must-roster player at this point.

Deep-league target: Jacob Wilson , Athletics (26%) – When Wilson got the call to the majors, he came with a decent amount of hype after a ridiculous season that saw him hit .438 with just 13 strikeouts in 46 games in the minors. Then he got hurt in his first major-league game and still doesn't have a timetable to return. Here's hoping it's relatively soon, and if you have a roster spot to play with, I like the idea of getting ahead of his return, because there's still difference-making potential here, especially with the A's lineup looking great lately.

Outfield

Kerry Carpenter , Tigers (54%) – Carpenter began his rehab assignment earlier this week, which means he might be pretty close to coming back from the back injury that has had him on the IL since late May. Back issues are scary, and Carpenter's recovery from this injury has been tough, but you might have forgotten that he was hitting .283/.342/.572 in his first 50 games of the season – he also has 28 homers in 168 games while hitting .279 since the start of last season. That might just be a must-start Fantasy option.

Jesus Sanchez , Marlins (14%) – Sanchez has been putting up impressive underlying numbers all season, but is only just recently actually making an impact in games. He is hitting .256 since the start of July, but with a 30-plus homer pace and the underlying numbers to back it up.

Jake McCarthy , Diamondbacks (26%) – McCarthy isn't quite an everyday player, but he's forcing the Diamondbacks to at least consider it by hitting .367/.397/.633 with a near 30-steal pace since the All-Star break. He probably doesn't need to be rostered in points leagues, but McCarthy looks quite valuable in any categories league.

Masataka Yoshida , Red Sox (61%) – Yoshida's skill set is a weird one for Fantasy, because he's usually best suited for points leagues, which are the shallower format, where he is often too fringe-y to really matter. But when he's hot, Yoshida tends to get really hot, and he's hitting .318/.384/.500 since the  start of July while starting all but four games and putting up a 140-RBI pace. That won't prove sustainable, but Yoshida is a viable option in all formats when he's this locked in.

Matt Wallner , Twins (22%) – Wallner was so bad early on this season that he earned a trip back to the minors, and yet he is still hitting .256/.379/.545 since the start of last season, with 21 homers in 110 games. There are massive strikeout issues here as well as a platoon role, but also huge power that is worth using in categories leagues, at least.

Starting pitcher

Spencer Arrighetti , Astros (45%) – 7 IP, 2 H, 2 ER, 1 BB, 13 K – He's the full list of pitchers with consecutive starts of at least 12 strikeouts this season: Spencer Arrighetti. That's it, that's the full list. Arrighetti has flashed significant strikeout upside all season, but is only just now starting to show consistent command to take advantage of it. Over his past six starts, he has a 3.25 ERA (3.34 FIP) with 49 strikeouts and only 11 walks in 36 innings of work, and that doesn't count another 10-strikeout outing a few starts before this stretch. This upside is impossible to ignore now.

Tobias Myers , Brewers (63%) – Myers has been keeping runs off the board well all season, but he has mostly done so without flashing much strikeout upside, so I haven't really been too interested in it. But he did strike out nine in his most recent outing, which covered 7.1 scoreless innings, lowering his ERA to the season to 2.79. It still comes with a 4.12 FIP, so I remain skeptical, but let's see if he can build on it.

Ryne Nelson , Diamondbacks () – 7.1 IP, 3 H, 2 ER, 1 BB, 9 K – Nelson now has nine or more strikeouts in three of his past five starts, a stretch that coincides with a chance in his approach to prioritize his four-seamer, especially up in the zone. I don't really believe in the overall profile for whiffs – he still doesn't have a pitch with a whiff rate over 21% for the season – but he is at least hot right now.

Jeffrey Springs , Rays (64%) – In his third start back from elbow surgery, Springs finally showed the upside we've been waiting for. He struck out eight over five innings against the tough Orioles , while walking none and giving up just one earned run. He had his changeup working splendidly for 10 of his 19 whiffs, and this is the first time he's really looked like the difference maker we thought he might be before his injury last season. Let's see if he can build on it.

Jose Soriano , Angels (46%) – When he's going right, Soriano kinda looks like a right-handed Framber Valdez : He's an elite groundball pitcher with iffy command at times and the ability to get strikeouts when his curveball is working. He's on a decent run right now, allowing just one earned run in his past two starts with 13 strikeouts to just three walks, and I think he should continue to be a solid starting option moving forward as long a she keeps the walks in check.

Martin Perez , Padres (20%) – 7 IP, 3 H, 2 ER, 2 BB, 6 K – In two starts since joining the Padres, Perez has completely changed his approach, trading out a bunch of cutters and sinkers for more changeups and curveballs, which have become his two most-used pitches. Those are his best swing-and-miss pitches and, not coincidentally, he has struck out 13 in 13 innings; he had just 13 in 21.2 innings in four July starts with the Pirates . I think we know enough about Perez to not assume he's suddenly going to be a difference maker, but he's certainly had stretches where he can be a very useful Fantasy option in the past, and it looks like he might be in the middle of another.