WASHINGTON -- The Nationals placed center fielder Victor Robles on the 10-day injured list with back spasms for the second time this season Wednesday, a day after Washington starter MacKenzie Gore questioned Robles' effort on a fly ball that fell for a single.

Washington selected the contract of outfielder Derek Hill from Triple-A Rochester to replace Robles on the roster. Robles was sidelined by back spasms from early May until this past Friday. He had started five straight games since his return.

Manager Dave Martinez said Robles told him after Tuesday night's loss to St. Louis that his lower back was bothering him while running. Robles also got a poor jump on a deep fly ball on Monday that glanced off his glove for a triple. Robles skidded into the center-field wall after failing to make the grab.

"The more I watched him, the more I watched his jumps and stuff, something didn't look that right, but he kept telling me he was fine," Martinez said. "After last night I wanted to really sit down with him and talk to him and get out of him exactly what I thought he'd say."

Gore and Robles exchanged words in the dugout after a line drive off the bat of Cardinals rookie Jordan Walker fell in front of the center fielder for a second-inning single. Gore allowed five runs in six innings to take the loss as the last-place Nationals lost their fifth straight and 13th of 15.

"Obviously, MacKenzie thought he should have caught the ball," Martinez said after the game. Gore said the players had resolved their differences.

Hill was signed as a minor league free agent in the offseason after three seasons with the Tigers. He suffered a hamstring injury in spring training. The 27-year-old was batting .320 with eight homers and 31 RBIs in 52 games in High-A and Triple-A.

"I feel like I bring a lot of energy," Hill said. "A lot of hustle doubles, stealing bags, running stuff down in the outfield. Just trying to be that hustle guy."

The Nationals also placed right-handed reliever Carl Edwards Jr. on the 15-day IL, retroactive to Tuesday, with right shoulder inflammation and recalled lefty Joe La Sorsa. Washington did not have a left-handed reliever on the active roster before the move.