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7/22/2013 8:22 P.M. ET

Marquis out for season due to elbow injury

MILWAUKEE -- Padres pitcher Jason Marquis will miss the remainder of the season after it was determined on Monday that he has significant damage to the ulnar collateral ligament in his right elbow.

Manager Bud Black said Marquis met earlier Monday in Cincinnati with Dr. Timothy Kremchek, the Reds' medical director and chief orthopedic surgeon. The two have a long-standing relationship, Black said, as Kremchek once removed bone chips from Marquis' elbow.

"The doctor feels as though it's significant," Black said of Marquis' injury.

Marquis allowed six runs on eight hits with three walks over 5 1/3 innings in a loss to the Cardinals on Friday as he was hit hard and his velocity was down slightly from where it typically is.

It hasn't been determined if or when the 34-year-old Marquis will have surgery to repair the ligament. He is on a one-year deal worth $3 million, which likely means he has thrown his final pitch for the Padres.

Marquis was 9-5 with a 4.05 ERA in 20 starts this season. He was 9-2 with a 3.63 ERA in his first 14 starts and the team was 10-4 in games he started. But he never got that elusive 10th victory, going 0-3 with a 5.13 ERA over his last six starts.

"You look at the win-loss record and the overall ERA, though it has been climbing as of late, and we won a lot of games he started," Black said.

Right-hander Sean O'Sullivan will start in place of Marquis on Wednesday against the Brewers.

Ross excited to rejoin Padres' rotation

MILWAUKEE -- The question made Padres pitcher Tyson Ross laugh on Monday.

Did he ever think he'd be peppered with so many questions about his hitting?

"Never," he said, smiling.

A strained left shoulder injury that he sustained in April -- while getting a hit off the Dodgers' Clayton Kershaw, no less -- essentially sidetracked Ross' early season, though he's finally set to jump back into the team's starting rotation.

Ross will be added to the team's 25-man roster before making a start on Tuesday against the Brewers at Miller Park. It will be his first start since April 17.

"It was unfortunate I had an injury early in the season, but I'm excited about getting back in the rotation and starting every fifth day," Ross said.

Ross, who began the season as the team's fifth starter, suffered a subluxation to his left (non-throwing) shoulder swinging a bat against the Dodgers. He missed 14 games while recovering and then rejoined the team as a reliever.

The Padres optioned Ross to Triple-A Tucson on July 9 to build his endurance and pitch count with the intent of sticking him back in the rotation. That opportunity will come Tuesday.

Ross threw 62 and 70 pitches in his two games in Tucson and manager Bud Black feels he can throw in the 90-pitch range at this point.

Ross went as far to retool his swing with hitting coach Phil Plantier to take stress off his shoulder so he doesn't suffer a similar injury.

"His arm is strong ... he feels good," Black said. "The two starts [in Tucson] set him up for this start."

Ross didn't just build his endurance in Tucson; he worked on his changeup to give him a third pitch to add to his fastball and slider. Ross used it a lot, he said, and intends on doing so Tuesday and moving forward.

"I wasn't able to use it much coming out of the bullpen because you don't want to get beat with your third pitch," Ross said. "The first couple I threw in a game [in Tucson] were not that great. But if I threw a bad one, I'd come back and throw another one."

Ross went 0-1 with a 3.86 ERA in three starts before he was injured. As a reliever, he went 0-3 with a 3.48 ERA over 19 appearances.

Sampson named Texas League Pitcher of the Week

MILWAUKEE -- Padres Minor League pitching prospect Keyvius Sampson continues to enjoy a strong month, and Monday he was named the Texas League Pitcher of the Week.

Sampson allowed one hit and two walks and tied his career high with 12 strikeouts over seven shutout innings against Midland on July 20 for Double-A San Antonio.

Sampson, a 22-year-old right-hander, is 7-1 with a 2.27 ERA since May 16. Overall, Sampson is 7-4 and has a 2.67 ERA in 16 games (15 starts) with San Antonio. He has 94 strikeouts over 84 1/3 innings with the Missions.

Part of Sampson's success can be attributed to his improved slider, which has become a very good pitch for him this season. He was named the Padres' Minor League Pitcher of the Month for June after going 3-1 with a 2.20 ERA in six games.

Sampson was selected by the Padres in the fourth round of the 2009 First-Year Player Draft.

Corey Brock is a reporter for MLB.com. Keep track of @FollowThePadres on Twitter. This story was not subject to the approval of Major League Baseball or its clubs.