The club did not have to DL Curtis Granderson, who is day to day with general soreness after crashing into Chase Field's right-field wall.
"That's the game," Nieuwenhuis said. "It stinks that Juan goes down, [Granderson] gets hurt, but that's the game. That's probably the worst part of the game is injuries happen, and you've got to keep going as a team."
The Mets waited until less than an hour before Tuesday's first pitch to make the DL move official, subjecting Lagares to further medical tests including an MRI. The MRI revealed the strain.
More fortunate than Lagares was Granderson, who avoided the DL after crashing into Chase Field's fence. Though still too sore to play in Tuesday's game against the D-backs, Granderson said he might be available to pinch-hit, and he could return to the starting lineup as soon as Wednesday.
But with a matinee scheduled Wednesday and an off-day after that, a more conservative approach would net Granderson three full days of rest prior to Friday's series opener against the Braves at Citi Field.
"I was surprised when I got up [Tuesday] -- even walking around was a lot better than I thought it was going to be," said Granderson, who is batting .170 with one home run in 13 games. "And then as I continued to warm up and go through treatment and all that good stuff, things are feeling a lot better."
Nieuwenhuis, 26, was batting .310 with two homers and eight RBIs in 10 games at Vegas. He has appeared in 138 career games with the Mets, hitting .236 with a .672 OPS.
Nieuwenhuis will replace Lagares, 25, who was the Mets' best player over the season's first two weeks -- batting .314 with an .816 OPS and a team-high seven RBIs, all while playing his usual Gold Glove-caliber defense in center. Lagares had never previously suffered a hamstring strain before feeling something pull on his way to first base in the seventh inning Monday.
Manager Terry Collins spoke Tuesday of the difficulty in replacing Lagares, though the Mets are confident Nieuwenhuis can do the job on a short-term basis. Lucas Duda made an appearance in left field Monday after both Granderson and Lagares suffered their injuries, but the Mets do not wish to use Duda at an unnatural position if they do not have to.
"We've seen in the past where I thought his offense has struggled a little bit because he's so concerned about playing left field or playing right field," Collins said. "He's so comfortable at first."