Paul Molitor wants reinforcements for his roster when the Twins return to action Tuesday. The calendar may limit how many he gets for a while.

First baseman Kennys Vargas, shortstop Danny Santana, catcher Eric Fryer and righthanded relievers Michael Tonkin and A.J. Achter will be at Target Field on Tuesday, the first wave of arrivals from Class AAA Rochester.

More are expected to join the team once minor league seasons end next Monday or, in the case of Class AA Chattanooga, after the Southern League playoffs.

Top pitching prospect Jose Berrios allowed a solo home run to Pawtucket’s Chris Marrero, but allowed no other runs over six innings Monday, striking out five and walking none in Rochester’s 4-2 victory. General Manager Terry Ryan was in attendance to watch, but it’s not clear if Ryan intends to promote Berrios this month.

The 21-year-old Puerto Rican has pitched a career-high 161 innings this season and is not on the 40-man roster, so promoting him would require waiving a player.

After Monday's start, Berrios told the Rochester Democrat and Chronicle that he hasn't yet been told what's coming.  “I don’t know; I’m waiting for something,” he said. “If they call me up, I will thank God.”

If he doesn't get called up, Berrios added: “I respect the boss and the decision.”

Major league rosters can expand to 40 on Sept. 1, but unlike last season, the date doesn’t coincide with the traditional Labor Day end to the minor league season.

Still, “there is definitely at least part of the final package that we want to see here” right away, Molitor said, so that foursome, all of whom have spent time with the Twins this season, were summoned immediately after Monday’s game in Rochester, N.Y.

Tonkin, who has yo-yoed between Rochester and Minneapolis all season, will be making his fifth stint with the Twins. He adds depth to a bullpen that has shouldered a heavy workload. Fryer’s presence alleviates any worries about catching injuries. Vargas gives the Twins a power hitter on the bench, and Santana, who can play infield and outfield, was one of the team’s most valuable hitters a year ago.

Fryer is not on the Twins’ 40-man roster, so a spot must be cleared on Tuesday, presumably by waiving another player, before he can join the team. The only other catcher on the 40-man roster is Josmil Pinto, but Molitor ruled out choosing him as the third catcher, because concussions kept him from playing the position this season.

The four immediate call-ups have all performed well in Class AAA. Santana is hitting .311 with two home runs in 34 AAA games, while Vargas is a combined .283 at Chattanooga and Rochester, with 13 home runs and 69 strikeouts in 72 games. Tonkin owns a minuscule 1.10 ERA and 14 saves in 33 appearances for the Red Wings. Fryer has batted .292 at Rochester.