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SAN DIEGO -- The Giants didn’t make any free-agent additions to the bullpen over the offseason, but there are still several new faces who will have a chance to make significant contributions this year.

Injuries to Ethan Small (right oblique strain), Sean Hjelle (right elbow sprain) and Luke Jackson (lower back strain) opened the door for three rookies to earn relief spots with the Giants over the first two days of the regular season. Here’s a look at how the young trio could fit into the club’s bullpen mix in the coming weeks:

Landen Roupp, RHP (Giants' No. 12 prospect)

After missing a sizable chunk of last season with a back injury, Roupp was supposed to be limited to throwing bullpens in his first big league camp with the Giants. But his outlook began to change after he impressed the coaching staff with his mid-90s sinker and signature curveball, which is viewed as the best breaking ball in the organization.

Roupp, 25, had never pitched above Double-A Richmond and logged only four Cactus League appearances this spring, but he started to suspect that he might have won a spot on the Opening Day roster after the Giants scratched him from his scheduled exhibition outing against the A’s on Tuesday.

“They told me I was throwing a 'pen,” Roupp said. “Then it kind of set in. I was like, ‘I have a chance.’”

Roupp ended up being the last player to find out he made the team and admitted that he “kind of blacked out” when manager Bob Melvin delivered the news after the game.

“I never would have thought it would happen,” Roupp said.

He earned that spot.

“At this point in time, we feel good enough about bringing him here,” Melvin said. “We’ve seen the stuff. We’ve seen the swings against him. We’ll see how the nerves are early on in a Major League season, but he performed well enough to make the team.”

The Giants view Roupp as a starter in the long run, but he’ll have to adjust to working out of the bullpen early this season. He didn’t seem too fazed by the transition on Friday night, though, when he posted a scoreless inning in his Major League debut against the Padres at Petco Park.

“He’s really poised,” catcher Joey Bart said. “If he didn’t have that kind of composure, I don’t know that he’d be ready. But when I’ve been around him, the way he attacks hitters is impressive. It’s not like a young guy. It’s like, ‘I got a lot of confidence.’”

Erik Miller, LHP (No. 30 prospect)

The Giants are relatively short on lefty relievers, so it was a bit surprising to see Miller optioned to Minor League camp on March 11. The club told Miller it wanted him to work on being able to throw multiple innings, but it soon became clear that he remained in the running for a bullpen spot.

“They were giving me hints throughout the weeks after that, giving me encouragement, saying it’s not over yet,” Miller, 26, said. “I could read between the lines.”

Small landed on the 60-day injured list on Thursday, so Miller should have plenty of runway to establish himself as the second lefty option behind veteran Taylor Rogers for now. Miller looked up to the task in his Major League debut on Thursday, striking out one over a 1-2-3 eighth inning while topping out at 98.4 mph with his fastball.

“Really good,” Melvin said. “I’m not sure I saw 98 [before]. I know it’s in there. Pretty excitable in his first outing. He went through it really well. He’s got the ability to get righties out and lefties out, so it was a really good first start for him.”

Kai-Wei Teng, RHP

Like Miller, Teng was added to the 40-man roster in November, but he ended up missing most of big league camp with an oblique injury. Teng was slated to open the season at Triple-A Sacramento, but he found himself making an unexpected trip to San Diego after Jackson went down with a back injury on Opening Day.

Teng recorded a 4.42 ERA across 29 appearances (28 starts) between Double-A Richmond and Triple-A Sacramento last season. He should be able to provide length out of the bullpen after pitching three innings in his final spring outing. The Taiwanese right-hander could be in line to make his Major League debut this weekend. His excitement level is already off the charts.

“If it’s [on a scale of] 1 to 10, it’s probably 15,” Teng said via interpreter Matt Chan.