Joe Ross will be activated on the 60-day disabled list Tuesday. (Jonathan Newton / The Washington Post)

The Nationals’ next batch of September roster moves will include the call-up of outfielder Victor Robles and the activation of starting pitcher Joe Ross, who has missed all of his season while recovering from Tommy John surgery he underwent in July of 2017.

Ross, 25, is a proven back-of-the-rotation starter who the Nationals have missed this season. He has made 45 starts across three major-league seasons in 2015, 2016 and 2017, and Manager Dave Martinez said Monday that the Nationals are still deciding how to use him this September. But whether Ross is coming out of the bullpen or getting starts in the coming month, he is expected to compete for a spot in the Nationals’ rotation next season. Ross made 13 starts in 2017 and finished with a 5-3 record and 5.01 ERA. He also started a playoff game for the Nationals in 2016, giving up four earned runs in 2 2/3 innings of work.

In his last rehab start with the Class AAA Syracuse Chiefs on Sept. 1, Ross gave up one run on five hits in 5 2/3 innings. He threw 89 pitches, his highest total of the summer, walked three hitters while striking out four.

“He’ll be available after tomorrow,” Martinez said Monday. “So we’re actually going to sit down after we talk and have a game plan and see what we are going to do here with him. There is a good chance he might start, we don’t know that yet.”

The Nationals’ trade of Gio Gonzalez opened a spot in the rotation, and that will be filled by Erick Fedde on Tuesday. Fedde, the Nationals’ top pitching prospect coming into this year, has missed the bulk of this season with a shoulder injury. The rest of the rotation includes Max Scherzer, Stephen Strasburg, Tanner Roark and rookie Jefry Rodriguez, so it is unclear where Ross slots in that group if the Nationals do want to get him starts.

Robles is one of the Nationals’ brightest prospects, and could have been called up earlier this season if not for an elbow injury. Martinez said Monday that he expects Robles to get opportunities in the outfield, and both Ross and Robles illustrate the approach for the month ahead: With the Nationals under .500 at 68-69, and with dwindling mathematical chances to make a surprise postseason run, young players will get chances to prove themselves.

“What I want to see, I want to see some of the younger guys play, I want to see them in high-leverage situations,” Martinez said. “I want to see what they do and see what we have for the future. I really do.”

LINEUPS

CARDINALS (76-61)

Matt Carpenter 3B

Yairo Munoz RF

Matt Adams 1B

Marcell Ozuna LF

Paul DeJong SS

Greg Garcia 2B

Harrison Bader CF

Francisco Pena C

Jack Flaherty P

NATIONALS (68-69)

Adam Eaton RF

Trea Turner SS

Bryce Harper CF

Anthony Rendon 3B

Juan Soto LF

Ryan Zimmerman 1B

Wilmer Difo 2B

Pedro Severino C

Max Scherzer P

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