Brad Miller felt a tweak Saturday afternoon in his rib cage that could become what Joe Girardi labeled a “significant” loss if the injury proves severe.

Miller, a versatile reserve, was scratched 10 minutes before a 9-3 win over the Tigers after injuring himself during his pregame sprints. The Phillies signed Miller just before camp to be a left-handed hitter off the bench who can play the infield and outfield corners.

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Girardi said after Saturday’s game that he could not provide a timetable for Miller’s return as the team was not yet sure how severe the injury was. Miller will not play Sunday, the manager said. The season starts in less than three weeks and rib cage injuries can often linger.

Losing Miller, who had a .807 OPS last season with the Cardinals, would be a blow.

“Our hope is that it’s not long, he’s not going to miss much time, and we’ll get him back out there,” Girardi said. “But it’s significant because he’s dangerous with a bat in his hand and he gives us some flexibility and he allows guys to have some off days and you get a dangerous bat in there.”

If Miller’s not ready by April 1, his role on the opening day roster could be filled by Nick Maton or C.J. Chatham, utility players who have yet to reach the majors. Maton, 24, was a seventh-round pick in 2017 and Chatham, 26, was acquired this winter from Boston. Both have had good showings this spring and have handled multiple positions.

If Miller is healthy, the construction of the bench will depend heavily on who wins the everyday job in center field. If Scott Kingery is playing center, the Phillies will need a player like Chatham or Maton who can move around defensively.

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If it’s Odubel Herrera or Roman Quinn, then Kingery would be that super-utility bench player. But that competition continues to be lackluster as none of the three have separated themselves. Until that happens, it’s tough to draw up the bench.

“Our team is kind of in flux because of center field,” Girardi said. “When you put your arms around it, it kind of affects everything else you do.”

Eflin with an X

Zach Eflin was so efficient that he had to go to the bullpen for extra work after breezing through four innings. He threw just 39 pitches, 28 of which were strikes, and allowed two hits. Eflin struck out four and walked none.

Eflin has been excellent this spring as he prepares to enter the season as the No. 3 starter behind Aaron Nola and Zack Wheeler. He found success Saturday “playing the X’s.”

“It’s more about picking locations,” Eflin said. “Up and in to a lefty, low and in to a lefty, up and away to a lefty, down and away to a lefty. Play the same game with a righty. Sinker away, four-seam away, cutter away. There’s like four different paths you can take whether it’s a straight ball or one that’s cutting or sinking. You start mixing that up with low and in, low and away, up and in, up and away, it’s a completely different game.”

Extra bases

Bryce Harper homered, Didi Gregorius hit a grand slam, and Andrew McCutchen had two doubles. ... Seven of the nine batters in the starting lineup had at least one hit. ... Hector Rondon and Tony Watson, veteran relievers on minor-league contracts, logged scoreless innings to remain in the bullpen competition. ... Matt Moore will start Sunday in Bradenton, Fla., against the Pirates. The game will be carried by WIP-FM.