Christian Walker (oblique) exits Arizona Diamondbacks' win

Arizona Diamondbacks first baseman Christian Walker exited Monday's 9-8 walk-off win over the visiting Washington Nationals due to left oblique tightness.

After the contest, Arizona manager Torey Lovullo acknowledged his concern over the injury is "not minimal" as Walker awaits a further examination and imaging scheduled for Tuesday but that he hopes the veteran won't have to miss much time.

Kevin Newman replaced Walker at first base at the top of the fourth inning.

It was unclear when Walker was injured, but in the third inning, he made a long run down the first-base line and into foul territory to catch a pop by Ildemaro Vargas . After the grab, Walker quickly turned to throw the ball back to the infield.

Walker struck out in his lone at-bat on Monday. Newman finished with two hits and an RBI. Corbin Carroll , who was pinch hitting for Newman in the bottom of the ninth, cracked a two-run homer to cap a five-run rally and push the Diamondbacks past the Nationals.

In 107 games this season, Walker is batting .254 and is tied for the team lead with 71 RBIs. His 23 homers rank second for Arizona.

The Diamondbacks enter Tuesday a half-game behind the New York Mets and the San Diego Padres , who are tied for the final two National League wild-card positions.

Information from Field Level Media was used in this report.