PORT CHARLOTTE, Fla. -- Early Thursday, the Phillies still operated as if they planned to play the Marlins on Opening Day on March 26.

So, before Major League Baseball announced it suspended Spring Training and postponed the beginning of the regular season by at least two weeks because of the COVID-19 pandemic, the Phillies discussed Aaron Nola’s chances to pitch the season opener and Seranthony Domínguez’s chances to pitch at all in 2020. Nola missed a scheduled start this week because of an illness, creating concern that he might not be ready by March 26.

Nola said he is fine and the originally scheduled Opening Day remained in play. Domínguez, however, faces more uncertainty after he felt tightness in his right elbow Sunday in a Grapefruit League game against the Blue Jays in Dunedin.

On Thursday afternoon, Phillies right-hander Jake Arrieta left the club’s game in the bottom of the fourth inning against the Rays with stiffness in his right shoulder. He said he is not concerned and added that he would “absolutely not” call it an injury. Arrieta said strength and range-of-motion tests afterward were fine.

“It could be a number of reasons for that, but just one of those days,” Arrieta said. “We’ll obviously be careful with it come tomorrow and see where we're at. I don’t expect to be set back at all.”

Domínguez is the more immediate concern. He suffered a strained ulnar collateral ligament last season. The Phillies acknowledged at the time that Tommy John surgery was a possibility. Domínguez said that he needed a “miracle” to avoid it. But highly regarded orthopedist Dr. James Andrews recommended a more conservative approach. Instead, Domínguez rehabbed in the fall and winter. He said he entered camp healthy.

Domínguez made two Grapefruit League appearances this month. He struck out two in two perfect innings and looked good in the process, but then Domínguez felt something in his elbow on the final pitch he threw Sunday.

“Right now, I think it’s less than last year,” he said. “Because last year, after I felt something, I still threw the next day. That's why I got more hurt. Now, I'm going to have to wait for the MRI to see what happens.”

Domínguez has been monitored and tested by the Phillies medical staff over the past few days. He will receive an MRI on Thursday. Those results are not expected until Friday at the earliest.

“He’s been responding pretty well to some of that therapy,” Phillies general manager Matt Klentak said. “At this stage, it’s premature for us to speculate on the severity. But I do think that it’s reasonable to think, at this point, to expect that Seranthony would be on the [injured list] to begin the year, but again, we don’t know yet what the long-term impact is going to be.”

If Domínguez misses a significant period of time, it would be a blow to a bullpen that considers him a closer-in-waiting. The Phillies signed only one relief pitcher to a Major League contract this offseason, inking Tommy Hunter to a one-year, $850,000 contract. Hunter is recovering from right elbow surgery, though he could be ready to pitch by mid-April. Right-hander Vìctor Arano also is recovering from right elbow surgery and shoulder soreness. The Phillies thought there was a chance he could be ready by March 26.

“We just have to wait and see on Seranthony,” Klentak said. “We’ll make it work. We have a lot of arms in camp competing for a spot right now. … I think between some starting pitchers that may shift to the bullpen, between returning Major League guys, between some kids in our system and some [non-roster invitees] that we have competing for jobs, I feel like we have a good mix of players to create a strong Major League bullpen.”

Nola said he had a stomach virus and not the flu. He said he never had a fever, so he was not tested for the flu or anything more serious. Nola threw a bullpen session Thursday.

“I feel good where I'm at,” Nola said. “I don't think it really messes too much up. Had it probably on a bad day, on my start day. I feel good. Before I got sick, I felt really good. My endurance was where it needed to be. It was pretty high for myself. I feel good.”