Chavez has no answers for the origin of his injury, though he believes it could have occurred while bracing himself for a comebacker that hit his hip in the sixth inning of Friday's outing in Texas. He was slightly sore the following day, but got through his Sunday bullpen session without any issues. Monday, Chavez said, "was my worse day."
"It's frustrating, because I don't know what happened," said Chavez, who has experienced trouble breathing, "and there's really nothing I can do."
It's been a season full of frustrating happenings, particularly for a starting rotation that already lost Jesse Hahn and Kendall Graveman to season-ending injuries. That list doesn't even include rehabbing pitchers Jarrod Parker and A.J. Griffin, who were expected to return midseason. Neither made a single start for the A's.
Furthermore, Chris Bassitt is working his way back from a bout of shoulder soreness.
"We've been hard hit all the way around this year. Certainly the starting rotation has been the hardest hit here recently," A's manager Bob Melvin said. "Some years you have more injuries than others. I know my first year [managing] in Seattle I had my 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."
Chavez had X-rays that were negative and is expected to return home as soon as Wednesday to undergo an MRI.
The right-hander finishes the 2015 campaign with a 7-15 record and 4.18 ERA, after pitching to a 3.40 ERA across 19 games -- 15 starts -- in the first half and a 5.59 ERA in 11 starts in the second half.
"His record certainly isn't indicative of how he's pitched, and he's conditioned himself to pitch a whole year, he's just going to get a couple starts short," Melvin said. "But I thought, all in all, he's pitched pretty effectively for us."
Martin, who last pitched Sept. 7 for Triple-A Nashville, allowed five runs on six hits in three innings against the Angels on Sept. 1. He was 5-7 with a 4.01 ERA in 18 games (17 starts) at the Triple-A level this year.
• Catcher Stephen Vogt (groin) did some tee work in the cage Tuesday and felt "not great, but pretty good," according to Melvin. There's still no timetable for Vogt's return.
• Outfielder Billy Burns (right hamstring) underwent a full range of baseball activity, but it remains uncertain that he'll he play in the White Sox series.
• Third baseman Danny Valencia was scratched from Tuesday's lineup with left trapezius muscle stiffness, while second baseman Brett Lawrie got a scheduled day off.