Oakland RHP Jesse Chavez sidelined by broken ribs

CHICAGO -- The Oakland Athletics' injury-wracked rotation got more bad news with the disclosure on Tuesday that right-hander Jesse Chavez will miss the rest of the season with a non-displaced fracture in his ribs on the right side.

"We're not really sure [how it happened], we think maybe on the ball that hit him on the hip the other day, maybe trying to brace himself on that," A's manager Bob Melvin said before Tuesday night's game. "We're not really sure."

This was Chavez's first relatively full season in a major league rotation, making a career-high 26 starts for the A's (surpassing the 21 he made in a swing role in 2014) and posting a 7-15 record with a 4.18 ERA while striking out 7.8 batters per nine innings.

Poor run support was cited as a key reason for his league-leading loss tally, with the A's averaging just 3.1 runs per 27 outs when he was in the game.

"I thought he's done pretty well," Melvin said about Chavez's first full season in the rotation." Early on we didn't give him any run support, but for the most part the first half was really good. There have been parts of the second half he pitched really well, too.

"His record is not really indicative of how he's pitched, and he's conditioned himself to pitch [as a starter] a whole year -- but he's going to come up a couple starts short. But all in all, he pitched really effectively for us this year."

That does not necessarily mean Chavez is a lock for the Athletics' 2016 rotation. An effective swingman, his role could ultimately depend on who else is on Oakland's roster.

"It's tough to tell right now," Melvin said. "The thing about Jesse, he's so versatile. But he's done enough to prove that he belongs in the rotation."

Chavez joins a list of starters lost down the stretch as injuries have decimated the A's rotation options. Starter Jesse Hahn has been on the shelf since July 1 and was transferred to the 60-day disabled list on Sept. 1 with a right forearm strain. Kendall Graveman joined him on the DL on Aug. 24 with a strained left oblique.

Both may not be back this season.

Chris Bassitt is also dealing with right shoulder soreness, and might make just one more start in the last three weeks of the season.

On top of that, neither Jarrod Parker nor A.J. Griffin was able to return from surgery to pitch for the A's this season.

"Some years, you have more injuries than others," Melvin said. "I know my first year in Seattle, I had five starters make every start the whole year. That has not been the case here this year. You do the best you can with it."

In the A's case, that means Cody Martin (0-1, 15.00) will return to the active roster to make his second start for Oakland on Wednesday night.

Martin was purchased from Atlanta on July 2 after making 21 appearances in the Braves' bullpen, posting a 5.40 ERA and 2-3 record.