Arizona Diamondbacks right-hander Merrill Kelly will miss his scheduled Opening Day start because of an intercostal nerve irritation, the team said on Wednesday.

Kelly was scheduled for additional testing Wednesday, including a CT scan, after he was scratched from a throwing session against hitters last week because of mid-back tightness.

Kelly, 37, was scheduled to start for the Diamondbacks in the regular-season opener against the host Los Angeles Dodgers on March 26.

"We've done pretty much every test under the sun that we can think of and everything's coming back clear, which is a positive," Kelly said on Wednesday. "Structurally wise, we've looked at the spine, we've looked at the ribs, we've looked at the muscles, we've looked at the tendons, we've looked at everything back there, and that's all coming back good, which is a positive, obviously. But there's still something going on back there. Still feel something. So we're just trying to turn over every rock and kind of look wherever we can to see what we can figure out about it."

Manager Torey Lovullo has not named a replacement starter for Opening Day, nor has he placed a timeline on Kelly's return to action.

"I saw it as kind of my one shot to throw Opening Day," Kelly said. "And obviously that's disappointing, but injuries are part of it, and all I really care about at this point is being able to throw again and then be ready for the team whenever, whether it's Opening Day or the last game of the rotation, doesn't really matter at this point as long as I'm back for it."

Kelly was a combined 12-9 with a 3.52 ERA in 32 starts for the Arizona Diamondbacks and Texas Rangers last season. He was moved to the Rangers at the trade deadline before he re-signed with the Diamondbacks in the offseason on a two-year, $40 million contract.

In seven major league seasons, the majority of which have been in Arizona, Kelly is 65-53 with a 3.77 ERA in 172 regular-season appearances (all starts).