NEW YORK -- The replace-Mets are about to more closely resemble the actual Mets.

The team activated three players from the injured list before Monday’s series opener in Arizona, including first baseman Pete Alonso, reliever Seth Lugo and outfielder Kevin Pillar. That dropped their number of players on the IL, which hit a season-high 17 earlier this week, to a more manageable 13.

• Injury & Roster Moves

Over the past few days, Alonso worked to convince the Mets that he did not need a Minor League rehab assignment. To that end, he tracked pitches in the bullpen, took batting practice off high-velocity machines, and completed all the defensive reps necessary to prove that his sprained right hand was no longer an issue.

The return of Alonso means one of their top offensive weapons is back in the lineup. After going 2-for-5 with a homer and four RBIs in Monday's 6-2 win, Alonso leads the Mets with seven home runs, seven doubles and 23 RBIs, to go along with a .242/.338/.455 slash line.

“Huge presence,” was how manager Luis Rojas described him. “I know [James] McCann has been a really good first baseman for us lately, but to have Pete in there, just the impact of his presence, it changes a lot of things. I think having Pete there can help guys like [Dominic Smith], can help guys even like Billy McKinney in the lineup, those lefties around him that he can protect. … His presence is definitely something that we need. If we hit for power, which is something that Pete can do, we can score a lot of runs.”

Lugo, who underwent surgery to remove a bone spur from his elbow in February, had always been scheduled to come off the IL on Monday, the first day he will be eligible. Although rain forced some changes to Lugo’s Minor League rehab assignment, preventing him from pitching on back-to-back days, he still took the mound four times for Low-A St. Lucie and Triple-A Syracuse, allowing one earned run over 4 1/3 innings.

Like Alonso, Lugo is one of the Mets’ most important roster pieces. He was the team’s best reliever from 2018-19, producing a 2.68 ERA with 207 strikeouts in 181 1/3 innings.

Far more surprising is the activation of Pillar, who underwent facial surgery after fracturing multiple bones in his nose when a 94 mph Jacob Webb fastball hit him on May 17. Pillar is coming off the IL just two weeks to the day after that incident.

The Mets optioned Sean Reid-Foley, Patrick Mazeika and Khalil Lee to Triple-A as corresponding moves and designated Cameron Maybin and Sam McWilliams for assignment.

Minor League outfielder Mason Williams was also selected to the Major League roster and active for Monday night's game.

Catching split

Alonso’s return will also affect the mix behind the plate, because McCann was playing first base most days in his absence. Rather than move back to catcher on a full-time basis, McCann will split time there with Tomás Nido, who has hit .323 with two home runs and eight RBIs over his last nine games. Nido earned the additional playing time based on that production, and despite the fact that he is making roughly $7.5 million less than McCann this season.

Rojas said that McCann might still fill in at first base on occasion, while also starting at least half the time at catcher.

Pitching matters

The Mets pushed everyone in their rotation back a day following Sunday’s rainout, resulting in a lineup of Jacob deGrom, David Peterson and Marcus Stroman for their upcoming three-game series in the desert. The team has a decision to make after that: Start Taijuan Walker as originally scheduled on Thursday in San Diego, or use Joey Lucchesi on Thursday followed by Walker on Friday.