Paul Molitor wants reinforcements for his roster when the Twins return to action Tuesday. The calendar may limit how many the Twins' manager gets for awhile.

First baseman Kennys Vargas, shortstop Danny Santana, catcher Eric Fryer and righthanded reliever Michael Tonkin will be at Target Field on Tuesday, a Twins source said 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.

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. That's half as many as were called up last Sept. 1, and the calendar is why.

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

Fryer is not currently 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.

Further additions are expected, though general manager Terry Ryan has not revealed who might be included.

Among players on the roster who are eligible to be called up in September are outfielder Oswaldo Arcia, though he is in the midst of an 8-for-75 (.107) August slump and is batting just .205 for the season; Chattanooga outfielder Max Kepler, a 22-year-old native of Germany who is enjoying a breakout season (.330, with 53 extra-base hits); shortstop Jorge Polanco, who has made three brief appearances with the Twins over the past two seasons; and Rochester pitchers Alex Meyer, Logan Darnell and Aaron Thompson, all of whom have spent time in the majors.

Jose Berrios, who allowed four hits, including a solo home run, over six innings in beating Pawtucket on Monday, is another potential candidate, but it's not clear whether general manager Terry Ryan, who was in attendance Monday, intends to promote the Twins' top pitching prospect this month. The 21-year-old Puerto Rican is 13-5 with a 2.90 ERA at two levels this season, but has pitched a career-high 161 innings and is not on the 40-man roster, so promoting him would require waiving another player. In addition, Molitor said Sunday that "I wouldn't expect" any pitcher other than Phil Hughes or the Twins' current five-man rotation to make a start over the Twins' final 32 games.

The four immediate call-ups have all performed well in Triple-A. Santana is hitting .311 with two home runs and 24 strikeouts in 34 Triple-A 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, and has allowed one earned run in his last 19 minor-league appearances. Fryer has batted a solid .292 at Rochester.