Phillies manager Joe Girardi said he is not terribly concerned, but with 15 days remaining before Opening Day, two of their starting pitchers cannot pitch because of back issues.

Right-hander Zach Eflin’s back flared up a little bit on Monday after his bullpen session. Girardi said Eflin is “day to day.” Right-hander Spencer Howard was sidelined on Monday, too, when he experienced back spasms.

Eflin, if healthy, is scheduled to pitch the Phillies’ third game of the season on April 4 against the Braves at Citizens Bank Park. The Phillies entered the spring planning to monitor Howard’s workload, which meant he could have opened the season anywhere from the rotation to the bullpen to Triple-A.

“We want to get Ef off the mound as soon as we can,” Girardi said following Wednesday’s 2-0 victory over the Tigers at BayCare Ballpark in Clearwater, Fla. “He played catch today, so we felt pretty good about that. We’ll just have to wait and see.”

So how concerned is Girardi about this?

“A little,” he said. “I like [that] there was a ton of progress the last few days and he was able to play catch today. That made me feel pretty good.”

There is no timetable for Howard.

“He’s still feeling those back spasms a little bit,” Girardi said.

If Eflin and Howard are slow to recover, right-hander Vince Velasquez will likely slide into the rotation. He entered camp competing with left-hander Matt Moore and right-handers Chase Anderson and Howard for the final two jobs, although Moore and Anderson have distinguished themselves with strong springs.

Iván Nova will start in Eflin’s place on Friday against the Yankees. Nova is a non-roster invitee in camp.

Too early to call Odúbel a frontrunner?

Odúbel Herrera hit his third home run of the spring in the fourth inning against right-hander Joe Jiménez. Herrera is batting .269 (7-for-26) with three home runs, six strikeouts and an .885 OPS. Roman Quinn went 1-for-2 with one walk. He is batting .318 (7-for-22) with two doubles, three walks, eight strikeouts and an .809 OPS. Scott Kingery went 0-for-2 with one strikeout. He is batting .111 (3-for-27) with one double, one home run, two walks, 12 strikeouts and a .432 OPS.

They are the top competitors for the job in center field with Herrera consistently having the best at-bats of the three. Mickey Moniak (1.257 OPS in 19 plate appearances) is a dark-horse candidate because he may need more time in Triple-A.

Adam Haseley had been in the mix, but he remains sidelined with a strained left adductor. Girardi said Haseley is progressing, but he gave no timetable for his return to action. Girardi initially estimated Haseley might miss four weeks, which would bring him to Opening Day on April 1.

“I think the next 10 days, two weeks are really important,” Girardi said about the center-field competition. “That’s kind of how I’m sizing it up. Quality at-bats are going to be really important. I’m just going to let it play out. There’s no rush to make the decision because they’re all getting at-bats and getting opportunities.”

On the clock: Wheeler dials in

Right-hander Zack Wheeler figured something was amiss following his last start, so before he pitched five scoreless innings against the Tigers, he stepped into the video room with a stopwatch, found a video from his last start and timed his windup from start to finish.

Wheeler knows what his time to the plate should be. It wasn’t that.

“Pitchers always have their checklist,” Wheeler said. “When something isn’t going right you go through that checklist. That’s one of the things: the timing and the movement. I noticed that my head was stepping away toward first base. I knew that was off. I know I’ve got to keep my head over my right foot just so I stay over the rubber and go straight to home, rather than all that movement. I’ve had that happen in the past, so I recognized it.”

Wheeler allowed four hits and struck out four in an impressive showing. He looks healthy and ready to pitch the second game of the season on April 3. He had surgery in October to repair his middle finger, which is prone to losing its nail. So far, so good.

“It’s there, it’s feeling good,” Wheeler said. “It’s a little sore every once in a while, but it’s to be expected. But it’s actually doing a lot better than I thought it was going to at this point, so that’s all I can really ask for. Hopefully it worked, right?”

Extra bases

• Girardi said he has not decided on a closer. Archie Bradley, Héctor Neris and José Alvarado are the most likely candidates. “That hasn’t been on our forefront of decisions that we have to make,” he said. “We really haven’t talked about it a lot. The makeup of the rest of the bullpen could affect how we do something. I think we have to figure that out, too.”

• Didi Gregorius got hit in the back of the head with a pitch on Tuesday. Girardi said he will be evaluated again on Friday.

• Catcher Rafael Marchan has not played since Feb. 28 because of a hamstring issue. He played in a simulated game on Wednesday. “He is progressing well,” Girardi said.