NEW YORK -- Rosters can expand next Saturday, and the Mets are going to have to decide whether their power-hitting first baseman at Triple-A Las Vegas will be part of the expansion plan.
Peter Alonso's name is under consideration by the Mets' decision makers, according to manager Mickey Callaway.
"We've discussed him, the pros and the cons of what we're trying to do with him, not only this year, but in the future," Callaway said before Saturday's game against the Nationals at Citi Field. "He's definitely a name we're discussing."
Callaway had said Friday that Jay Bruce would be getting a lot of time at first base the rest of the way to see if he could be the primary option there next season. Callaway also said Saturday that first baseman/left fielder Dominic Smith, who was sent down to Las Vegas Friday, would probably be back as a September callup. And Wilmer Flores started his team-high 68th game at first on Saturday.

But Alonso is intriguing. MLB Pipeline has him rated as the Mets' No. 2 prospect. His bat has accounted for a lot of production this season, as the 23-year-old righty hitter entered Saturday with a .278 average, 32 homers and 109 RBIs across 123 games with Las Vegas and Double-A Binghamton.
"I think we want to make sure he's developed and when he comes up here, he's ready to play at the Major League level," Callaway said. "It's not just about swinging the bat here. It's about defense as well. And we want to make sure he's in a good spot in his overall game and the things that we're going to value as an organization moving forward before we put him in that position."
Rosario a hit batting first
Amed Rosario sat atop the Mets' lineup card for the 31st time on Saturday. It has been his spot for the most part since the third week of July. Callaway has liked what he has seen since then from his 22-year-old shortstop.
"I think he kind of just instinctively is a little more patient when he leads off," Callaway said. "I think we've seen hitters like that in the past. I think Asdrubal Cabrera comes to mind when you moved him around. Whether it was leadoff or second or fifth, you saw a little bit different approach. And I think that Rosario is doing that as well."
Overall as a leadoff hitter, Rosario began the day batting .223 in 130 at-bats with four doubles, a triple, two homers and 15 RBIs. He had walked eight times and stolen nine bases in 11 tries.

Rosario also began the day second in the National League with nine steals since the All-Star break, and he was batting .303 with a .338 on-base percentage, three doubles, two homers, 12 RBIs and 12 runs scored in his previous 15 games.
"I think where we were at in the season, we wanted to see if he could handle it," Callaway said of the leadoff role. "I think he had made some significant adjustments already and was doing a pretty good job. … Now [Brandon] Nimmo was out for a while as well, so that kind of helped the decision. Ever since [Rosario has] been there, it's been a good test for him, and he's responded really nicely."
Back on Aug. 16 in the first game of a doubleheader in Philadelphia, Rosario hit a leadoff homer among his career-high four hits in a game that also came with a career-high four runs and a career-high tying three RBIs.

"I think there's also he's spent more and more time around Jose Bautista and has talked to him a lot, watched his ABs," Callaway said. "Obviously, Jose puts together a real nice patient at-bat, lays off some tough pitches, and I think that's also rubbed off on Rosie. So he's done a great job in that leadoff spot and I really like him right there."
Catching update
Kevin Plawecki started behind the plate for the second straight game on Saturday, but he's due to depart soon for the birth of his first child. Devin Mesoraco left Thursday's game against San Francisco with neck stiffness, but he has been available to catch on a limited basis. Tomas Nido was called up from Binghamton on Friday to have another catcher on hand.
"It's more muscular in nature," Callaway said of Mesoraco. "And it's something that a little medicine will probably help relieve, and it's gotten a little better so far where we feel confident he could go back there and catch an inning or two if need be. The biggest problem would be swinging at this point."