CHICAGO – The Rangers have some impressive young arms in their bullpen. Right-hander Rafael Montero is not one of them.

Yes, he has been impressive, but he is not “young.” He is 28 and spent four years in the big leagues with the Mets before he signed with the Rangers in the offseason. He missed all of last year while recovering from Tommy John surgery, but he may be the one success story among the four veteran pitchers attempting a comeback in Texas this season.

Drew Smyly and Shelby Miller are no longer with the team and Edinson Volquez is about ready to retire. But Montero has pitched his way into a meaningful role with the Rangers as their primary right-handed setup reliever.

He is the one still standing, now that Jesse Chavez is headed for season-ending surgery, Chris Martin was traded and Shawn Kelley has struggled since his return from the injured list on Aug. 7.

Since he was called up to the big leagues on July 23, Montero has pitched in 10 games and allowed just two runs in 16 2/3 innings. Opponents are hitting .186 off him with 11 hits, five walks and 19 strikeouts.

“He has shown us a lot,” Rangers manager Chris Woodward said before Sunday afternoon’s 2-0 loss to the White Sox at Guaranteed Rate Field. “Just right from the beginning, I put him in tough, high-leverage situations and he didn’t seem to be bothered by it one bit. He’s just making hitters look silly right now.”

Emmanuel Clase is the Rangers’ hardest thrower at an average of 99 mph. Jonathan Hernandez is next at 97 followed by Jose Leclerc at 96.7. Montero is right behind at 95.6. The separator for Montero over Clase and Hernandez is his past Major League experience with the Mets.

“You can tell [Montero] is a lot more calm,” Woodward said. “His stuff is just a little more precise. He’s got good stuff, he’s hitting 97 and 98, but [with] the command and the poise, he looks like he has been in the big leagues for a while. I didn’t know he was that good.”

He is. The Rangers have an extensive rehab staff working out of the Surprise, Ariz., complex led by medical coordinator Sean Fields and pitching coordinator Keith Comstock, and they were instrumental in getting Montero back to full strength, bolstered by the player’s determination.

“I used the tough moments to grind through it,” Montero said. “It made me a better player. It gave me motivation.”

Montero was a serious prospect with the Mets, rated as highly within that organization as some of the Rangers’ top young pitchers are now. He started in the Minor League system in 2011 and won the Pitcher of the Year Award for his team in each of his first three seasons. He was named to Baseball America’s First Team Minor League All-Stars in 2013.

Montero pitched for the Mets from 2014-17, making 30 starts and 28 relief appearances, going 6-16 with a 5.38 ERA and a 1.70 WHIP while dealing with arm injuries. He missed most of 2015 with rotator cuff inflammation. Now he is healthy and in the right role.

He has started before, but the Rangers see him as a multi-inning reliever. A pitcher can’t make an Opening Day roster based solely on 10 impressive appearances, but the Rangers are putting Montero through the test and, so far, he is acing it.

“When I signed here, they made me no promises,” Montero said. “All they did was give me the opportunity. I feel like this is a new start to my career.”

Rangers agree with Lora

The Rangers have reached a formal agreement with outfielder Bayron Lora from the Dominican Republic. MLB.com’s Jesse Sanchez first reported the signing in July. The Rangers have not announced the signing because it is still pending a physical. Lora, an international free agent, agreed to a $3.9 million signing bonus.