PORT ST. LUCIE, Fla. -- Todd Frazier was visibly upset as he left the Mets' clubhouse on Tuesday, bound for New York and another doctor's office. The knowledge was still fresh that Frazier had sustained a left oblique strain during batting practice the day before, depleting the Mets' infield depth and putting Opening Day in jeopardy.

"I thought I was doing everything right," said Frazier, who twice landed on the disabled list last season after avoiding it for the first seven years of his career. "It's just one of those things that happens, I guess. I'm frustrated. I'm very frustrated myself. It's just one of those things where you come into the year all healthy, ready to roll, and this happens. It's not fun."

The injury comes less than a week after the Mets diagnosed Jed Lowrie with a sprained capsule in his left knee, lopping two third-base options off the Mets' depth chart. The team still boasts plenty of depth at the position, from Jeff McNeil to J.D. Davis, Adeiny Hechavarria and others. But if the injuries to Frazier and Lowrie linger, it will force the Mets to dip into their assembled stockpile sooner than expected.

"As camp goes forward, we'll have a little bit better handle on timelines and the activity level for these guys," general manager Brodie Van Wagenen said. "But this was part of the design, to make sure we had versatility and depth to cover really whatever came our way."

Frazier's injury occurred without warning. In an attempt to stay healthier this season, the veteran did not appear in any of the Mets' first three Grapefruit League games, limiting himself to the back fields to ramp up slowly. But while taking part in live batting practice Tuesday, Frazier felt a pull on his left side. He went to a local clinic for an MRI, which revealed the strain.

"It wasn't just one swing, it was overall going through the at-bats yesterday," said Frazier, who batted .213 with 18 homers and a .693 OPS last season. "I hit a home run, hit a couple doubles. That's the weirdest part of it. It's just a strain of the left side. We've got to keep working on it."

While both Frazier, 33, and the Mets were careful not to put a timeline on the injury, oblique strains often take four to eight weeks to heal. The former timetable could have Frazier ready for Opening Day, but the latter would not.

If the injuries to Lowrie and Frazier linger, they will have a trickle-down effect on the rest of the roster. At third base, the Mets could turn to McNeil, a natural infielder who has been almost exclusively playing left field this spring. Van Wagenen said the Mets will stick with McNeil in the outfield for now, but could shift him in March if the situation warrants it.

In the short term, the Mets will use Hechavarria and Davis most often at third base, with T.J. Rivera, Luis Guillorme and Dilson Herrera all capable of playing there as well. Of that group, only Rivera and Guillorme were on the roster at the start of the offseason, pointing to the Mets' commitment to adding infield depth this winter.

"Every good team has depth," Van Wagenen said. "As we've seen here so far in camp, there are going to be guys that are on different timelines, schedules, and you have to have people that can step up, and play not only at a high level but also can play multiple positions. Fortunately, we have that."

The injuries also increase the likelihood that top prospect Pete Alonso could make the team as the Mets' Opening Day first baseman. With Lowrie in camp, Frazier had been slated to receive significant reps at first this spring; his long-term absence would leave Alonso and Dominic Smith as the Mets' primary candidates to man that position.

For now, all of it is mere speculation. Frazier will receive a cortisone injection in his midsection this week, with designs on returning before long. Lowrie is already back in camp, aiming to begin baseball activities soon. The Mets are hopeful both can contribute on Opening Day, even if they're uncertain about it.

"Not the best start," Frazier said, "but luckily it happened here in Spring Training, and we can nip this thing in the bud and get ready for the season."