ST. LOUIS -- After a respiratory scare and a night at the hospital, Cardinals closer Carlos Martínez was back at Busch Stadium on Monday and said he would be ready to go if needed for the series opener against the Nationals.

And ready he was, throwing just two pitches to get Ryan Zimmerman to line out and recording the final out of a 4-2 win.

“Everybody said his catch looked good, he said he felt great,” manager Mike Shildt said. “He said, ‘I got two tonight.’ Turned out he had two pitches. But it was good to have him back, on a lot of levels.”

Martínez experienced breathing problems and chest tightening when the team was in Denver last week but thought the symptoms would go away. He dealt with something similar previously, although he said it was worse this time.

After he had the same issues warming up on Saturday night, he spent the night in the hospital and went home on Sunday afternoon. Diagnosed with a combination of asthma and allergies, he was treated for both and given medicine, and he said the doctors cleared him to play.

“I didn’t think it was the altitude [in Denver] because when I came here, I felt the same,” Martínez said through a translator prior to the game. “I didn’t tell anyone in Colorado because I thought it was going to go away, but when I came here, it was really hard for me to breathe.”

“It’s a combination of asthma and allergy,” Shildt added. “I don’t know which one takes precedent. They’re both part of the situation that has given him some problems.”

The good news for Martínez and the Cardinals is that he was feeling better when he arrived at the clubhouse on Monday. He hasn’t thrown since the problems began -- aside from his warmup on Saturday night -- so he played catch on the field before Monday’s game and said he felt back to normal.

“It was a scary situation for me,” Martínez said. “It hadn’t happened like that before. ... But I feel great. I feel like I normally do. I showed [Shildt] I feel better. Right now, I feel good, and I’m ready for tomorrow and the next day.”

Shildt said the relief of having Martínez back on the mound paled in comparison to seeing the 27-year-old acting and feeling like himself again.

“The first thing I learned when I got to see him for the first time is, he just looked better,” Shildt said. “He was just in a much better place. In Colorado, he wasn’t in great shape there. He was gutting it up a little bit, and then clearly took a turn for the worse when we came home. I’ve been with Carlos for almost 10 years now, so I saw him and just saw that he looks good.”

Sunday's loss showed how crucial Martínez is to the bullpen -- and how lucky they are that he’s back and ready to go after missing just one game. John Gant walked three of the four Brewers he faced to set up Ryan Braun’s go-ahead grand slam off rookie reliever Junior Fernandez. If Martínez -- who has not allowed a run since Aug. 18 (10 appearances) -- had been available, things might have been different.

“I don’t think there’s any question about [how important Martínez is],” Shildt said. “It just puts everyone in the right spot. You look at bullpens, think about it front to back or back to front, but any way you look at it, there’s got to be an anchor. We’ve been blessed to have anchors this year with Jordan [Hicks] and now Carlos.”