SAN FRANCISCO -- The ball left Mike Yastrzemski’s bat at 87 mph, but when you’re standing 60 feet 6 inches away it may as well be 120 mph, because Ryne Nelson had no time to react.

The D-backs right-hander tried to get out of the way, but the ball struck him in his right elbow and kicked towards first base. Somehow, Nelson maintained his poise and chased the ball down and underhanded it to first baseman Christian Walker for the final out of the second inning.

Nelson clearly was in tremendous pain as he grabbed his arm. He would throw no more pitches Thursday night, as the D-backs went on to fall, 5-0, to the Giants at Oracle Park.

The question now is when the right-hander will throw his next pitch. X-rays taken during the game showed no fractures, but after the game his elbow was still very swollen and red seam marks from the baseball were still clearly visible.

“It’s a little stiff right now,” Nelson said. “Yeah, it doesn't feel too great, got hit right in the sweet spot. Right on the elbow, so we just want to see how it feels in the morning, give it some rest. We’ll know more tomorrow.”

The D-backs already had a roster decision to make on Friday, and Nelson’s situation should complicate it a bit -- and quickens the timeline.

Lefty Jordan Montgomery, who was in San Francisco on Thursday, will be activated in time to start Friday’s game in his team debut, and the D-backs will need to make a corresponding roster move. While that had figured to be lefty Logan Allen, who was called up prior to Wednesday’s game against the Cubs at Chase Field, they may want to hang onto him to start in Nelson’s place if he has to go on the injured list.

Allen was in the bullpen when Nelson got hurt and immediately started stretching, knowing that as the long man in the 'pen he would likely get the call if Nelson couldn’t continue.

Allen came on to start the third and allowed a run, but then held the Giants scoreless until departing with two outs in the seventh. An impressive outing, especially considering the circumstances.

“He was fantastic,” D-backs manager Torey Lovullo said. “We were in a position to win the game in the eighth inning with a one-run deficit all because of him. He was unbelievable, and without him we would have no chance. So a lot of credit goes to him.”

Allen, who signed a Minor League deal with the D-backs last December and was a non-roster invite to Spring Training, had been pitching well with Triple-A Reno, compiling a 3.00 ERA in three games (two starts) before getting called up.

On Thursday, Allen allowed three hits in the third but no more the rest of the game, finishing with 4 2/3 innings of much-needed relief.

Allen utilized his changeup well. It’s a pitch that was working for him in Reno, and it’s not your usual changeup, but more of a split-change that he throws out of a split-finger grip. He threw the pitch 16 times, getting 10 swings on it, generating five whiffs.

The D-backs' offense didn’t do much to help Allen out, as Logan Webb shut them down for seven innings. Webb allowed back-to-back singles to open the game and then retired 19 straight batters before issuing a one-out walk in the seventh.

“Webb had it going today,” Lovullo said. “And there was there was a lot of weak contact and I respect their starting pitcher, but I believe enough in our guys to be able to slug against anybody. So we have to find a way to zero in on the pitch we’re looking for and not miss it.”