Michael Smith is adamant the Mets should not have let Noah Syndergaard pitch without an MRI, while Jessica Mendoza doesn't think the MRI would have prevented his lat injury. (1:37)

Reeling from the team's latest injury, New York Mets general manager Sandy Alderson said it was his decision to let Noah Syndergaard start Sunday, despite the pitcher's refusal to have an MRI on his shoulder and arm before taking the mound.

"It was my decision for Noah to pitch with input with [a] variety of different sources," Alderson said Monday. "The MRI was not dismissed out of hand, and we had to evaluate the situation. ... From the overall standpoint, it is not to say things couldn't have been done differently. From my standpoint, I made the decision."

The Mets put Syndergaard on the 10-day disabled list Monday after an MRI revealed a partial tear of his right lat muscle. The Mets say there is no timetable for Syndergaard's return, but Alderson said, "I think it's going to be a considerable amount of time." Mets left-hander Steven Matz missed two months with a similar lat injury in 2015.

Noah Syndergaard (1-2) allowed five runs on five hits in the first inning of Sunday's 23-5 loss to the Nationals. AP Photo/Nick Wass

The ace right-hander was pulled from his start on Thursday because of biceps and shoulder discomfort and had been scheduled for an MRI. But after Syndergaard threw a bullpen session Friday, he said he felt great and ready to go Sunday.

"I'm pretty in tune with my body," Syndergaard told reporters. "And that's exactly why I refused to take the MRI."

Alderson said Saturday that it is unusual for a player to refuse to get an MRI but said "I can't tie him down and throw him in the tube."

The general manager said Monday that he had been told there was no connection between the shoulder/biceps discomfort and the lat injury.

"The doctor has said there wasn't any connection, there isn't any connection, between what happened and a possible bicep injury. That's all I can go on," Alderson said.

Syndergaard (1-2) allowed five runs on five hits in the first inning of Sunday's 23-5 loss to the Nationals. He grimaced after throwing a second-inning strike to Bryce Harper and reached for his right armpit before leaving the field with a trainer and manager Terry Collins.

Talking about the loss of his top pitcher, Collins said, "You're allowed 24 hours to be upset, then you've got to move forward."

The manager cited the hero mentality as a factor in injuries, saying "These guys ... are with each other a lot. You hear a guy, 'Hey, we need you. We need you in the lineup.' .... That mentality is rampant -- not just on our team, it is rampant throughout all of professional sports, not just baseball. 'Hey, look, I'm a little sore, but you know what? My team needs me out there.' A lot of times, it leads to a more severe injury."

Alderson said he might accelerate his search for pitching help. "I said over the last few days we had looked at that possibility. I would say yes, this probably could accelerate that process.''

The Mets recalled right-hander Paul Sewald from Triple-A Las Vegas. Collins said the team needed another arm after the bullpen was exhausted in the lopsided loss to the Nationals. The Mets must find a replacement to fill Syndergaard's spot in the rotation by Friday. Collins said left-hander Sean Gilmartin and right-hander Rafael Montero are the top candidates to join the rotation. Gilmartin was recalled from Las Vegas on Friday.

The Associated Press contributed to this report.