The Nationals will be without Joe Ross for quite some time. (Alex Brandon/Associated Press)

CINCINNATI — Nationals right-hander Joe Ross has a full thickness tear of the ulnar collateral ligament in his right elbow and will undergo Tommy John surgery Wednesday morning, Manager Dusty Baker announced Saturday. The procedure will end the 24-year-old’s season and likely will cost him at least a portion, if not all, of the 2018 campaign.

Ross exited his start last Sunday at Nationals Park after 3 1/3 innings with what Baker called with “triceps tenderness” after his velocity precipitously dropped. The discomfort, however, stemmed from his elbow, and he underwent an MRI exam on it. He then got an MRI arthrogram, which uses dye for contrast to examine the inside of a joint, later in the week for further clarity. The decision was then made to have the surgery, which orthopedist Keith Meister, the Texas Rangers’ physician, will perform in Texas.

“We knew with the MRI that it was going to be serious,” Nationals General Manager Mike Rizzo said. “We just didn’t know to what degree. The arthrogram made it very clear on what happened to it.”

Ross missed time last season with a shoulder injury, but he hadn’t dealt with elbow issues as a professional. He was, however, shut down with elbow trouble in high school, according to Baker, who advised Ross to ask teammates who have undergone the surgery about the rehabilitation process.

“He took it as well as a young man can take it,” Baker said. “This is his first surgery. I told him — we had a long conversation today — and I told him that he has to go in with a positive outlook. The first one’s always tough, and I told him I had a number of them. You got to be in a proactive versus reactive [mind-set], and you have to go into things with a positive outlook.”

Rizzo said a timetable for Ross’s recovery won’t be determined until after the procedure. However long it takes, the Nationals will need a short-term replacement starting Tuesday against the Angels and probably one to fill the void at least to begin the 2018 season.

In the short term, Jacob Turner and Edwin Jackson, both of whom are with Class AAA Syracuse, are the likeliest options to start Tuesday in Los Angeles. Both right-handers pitched Thursday and, as a result, are on turn to make the start. Turner started and logged five innings. Jackson entered in relief and threw three innings.

Turner, 26, appeared in 18 games, starting two, for the Nationals before he was designated for assignment on July 1 to make room for Sammy Solis on the roster. He allowed six runs across 11 1/3 innings in those two starts. He had a 5.20 ERA in 27 2/3 innings out of the bullpen. In two starts since joining Syracuse, he has surrendered 10 runs, walked seven and struck out five in 7 2/3 innings.

The 33-year-old Jackson started the season in the Baltimore Orioles organization, pitching 12 games for their AAA affiliate before getting called up. He appeared in three games for Baltimore, allowing seven runs (four earned) in three games before he was designated for assignment.

The Nationals signed Jackson, who posted a 4.03 ERA in 31 starts for Washington in 2012, to a minor-league deal in mid-June, which Jackson can opt out of if he isn’t in the majors by Aug. 1. Jackson was sent to Syracuse, where he didn’t give up a run in his first four starts (17 1/3 innings). He allowed one on five hits in his three-inning relief appearance Thursday. Altogether, he has a 1.77 ERA in 40 2/3 innings with 39 strikeouts and 20 walks in the minors.

Baker said the Nationals will determine Tuesday’s starter Sunday, then fly him out to Los Angeles before the rest of the team gets there. Ross won’t be there. His season is over after pitching to a 5.01 ERA in 13 starts. He will be in Texas waiting to undergo a surgery that has become commonplace across baseball, with pitchers sometimes coming back better than before, though it still could derail a career.

Ross will remain in Texas to stay with his older brother Tyson, a pitcher for the Rangers who underwent major shoulder surgery last October. Baker said that should help him traverse this setback, psychologically. The manager hopes the candle he lit for Ross at a Cincinnati church earlier Saturday will, too.

“He’s going to be okay,” Baker said. “He’s going to be okay.”