This is Phillies number-one priority at trade deadline, according to ex-GM

Heading into the All-Star break, the Philadelphia Phillies are flying high. They own Major League Baseball's best record and a nine-game lead in the National League East.

With so much success this season, it's easy to think this Phillies team has it all. But good is the enemy of great, and for this team, success will only be judged based on postseason results. So with the trade deadline looming, the Phillies must be expected to pursue roster upgrades.

The outfield has been an area of concern for Philadelphia all season, and for the past few weeks, the starting rotation has appeared one body short. But according to one expert close to the situation, there's an even bigger need for the Phillies to address at the deadline.

Ruben Amaro Jr., Phillies general manager from 2009-2015 and current analyst for NBC Sports Philadelphia, was asked to name the number one area of improvement for the Phillies at the trade deadline. He said adding one more arm to the bullpen was his top priority .

"(I) would love to see one more dependable 8th or 9th inning arm that Topper can trust. This completes an already phenomenal club – and dare I say – bullpen as well," Amaro said.

As Amaro indicates, there are lots of talented arms in the Phillies' bullpen already. Matt Strahm and Jeff Hoffman are headed to the All-Star Game, making the Phils the only team in MLB with two relievers represented this season.

Beyond those two, José Alvarado has been solid as the team's primary closer. Rookie Orion Kerkering has also been stellar, while Seranthony Domínguez and Gregory Soto represent experienced depth options.

However, it's also easy to see Amaro's point. Alvarado has never been a true closer before this season and both Strahm and Hoffman are having career years. As a team, the Phillies have 14 blown saves, tying them for 11th-most in all of baseball.

Options are numerous across the league, as relief pitchers are always easy to unload at the trade deadline.

The Miami Marlins' Tanner Scott and Los Angeles Angels' Carlos Estevez are widely expected to be dealt. Plus, there's always a chance the Oakland Athletics could sell high on flame-throwing closer Mason Miller.

When a team has championship expectations, it can't afford to lose games late in the postseason. The Phillies found that out firsthand in last year's NLCS, when Craig Kimbrel suffered back-to-back losses in Games 3 and 4 against the Arizona Diamondbacks.

The Phillies hope to avoid a similar fate in this year's postseason. And it just might take one more dominant arm to ensure they reach the promised land.

More MLB: The trade deadline acquisition Phillies "expect" to make, per insider