HOUSTON -- Something's not been right with Yankees left-hander Jordan Montgomery's throwing elbow for the past few days or weeks, not that anyone outside of the organization knew.

Other than saying he'd been treating this issue for "about two days," the big fella didn't specify how long he's been sore after a thrilling 4-0 Yankees win over the Houston Astros on Tuesday night that he was part of for a teeny bit.

Montgomery was the Yankees starter and called his seven-pitch, 1-2-3 first "probably the best inning I had this year."

Results wise.

Everything else about it was concerning.

His velocity was down from the usual low 90s to 88 mph and he says there was some forearm-elbow area arm discomfort "every other pitch" that was worse than he'd been feeling of late.

"It was giving me fits a little while," Montgomery said. "I thought I could throw through it. I've been doing a little extra treatment and little exercises. In college and the minor leagues, I've been able to grind through something like this."

The discomfort this time was alarming enough that Montgomery was totally truthful back in the dugout when pitching coach Larry Rothschild approached to see if anything was wrong after noticing the velocity drop.

"I couldn't let it rip honestly," he said. "I was 88, which is not horrible, but you want to go out there with your best stuff."

Hearing what was up right from the horse's mouth, the Yankees immediately made a call to their bullpen to tell rookie right-hander Domingo German to get up and get ready to pitch the next inning.

"It surprised me when they told me that German was coming into pitch," catcher Gary Sanchez said. "(Montgomery) threw a good first inning and a good bullpen in pre-game, so I was definitely surprised."

The Yankees' quick decision to end Montgomery's outing led to another quick one:

He'll return to New York on Wednesday to be examined by team doctor Christopher Ahmad, and depending on what tests show, the Yankees could be without their No. 5 starter for perhaps just 10 days or maybe a lot longer.

Montgomery's hunch is that his injury isn't serious even though elbow soreness often leads to worse news for pitchers. Asked for his level of concern, he answered, "Not too high. It's not like I'm hurting that bad. It's just kind of enough to be there and kind of scare you a little bit. I'm going to try to stay positive.

"Maybe I'll just miss a start. You never know. But I would be surprised if it was something real bad."

If Montgomery's issue is serious, he'd be a big loss. He was a godsend for the Yankees as a rookie last year, going 9-7 with a 3.88 ERA in 29 starts, and he's been pretty decent so far this season with a 2-0 record and 3.62 ERA in six starts.

While Montgomery is shut down - he'll probably be put on the 10-day DL on Wednesday - the Yankees will fill the rotation slot with German, a long reliever in his brief big-league career who has done a lot of starting in the minors.

German picked up Montgomery in a big way Tuesday working four shutout innings to give the Yankees a chance on a night in which they were shut out on three hits and 14 strikeouts for eight innings by Astros starter Justin Verlander before scoring four in the ninth off reliever Ken Giles, the big blow a three-run homer by Sanchez.

"If I have to start a game, I'll be ready," German said. "But they haven't told me anything yet. You can't get ahead of yourself. We'll see what happens."

Randy Miller may be reached at rmiller@njadvancemedia.com. Follow him on Twitter @RandyJMiller. Find NJ.com on Facebook.