ATLANTA -- The Twins have called up reliever Caleb Thielbar to pitch this week in Atlanta, but it's just a precursor to a more important move later this week, when they employ a new fifth starter in the rotation -- perhaps former first-round pick Kyle Gibson.For the moment, Thielbar makes history, once he makes his major-league debut, as the first member of the St. Paul Saints independent league team to play for the local big league team. The Twins optioned left-hander Pedro Hernandez, who had a 5.85 ERA in six starts, to AAA Rochester to make room on the roster.

Thielbar, who is from Randolph, Minn., had a 3.76 ERA in 17 relief appearances at Rochester. The 26-year-old was signed by Minnesota as a minor league free agent on Aug. 18, 2011, after pitching most of the seaso with the St. Paul Saints. The lefty had 34 strikeouts and eight walks in 26 1/3 innings for the Red Wings.

"He's throwing the ball very, very well," said manager Ron Gardenhire. "He's put together a nice string here. Not giving up too much of anything."

The move was prompted, Gardenhire said, by the series in a National League park, where he may be forced to pinch-hit for a pitcher a few times, and especially the lack of innings pitched by Twins' starters in the weekend series with Boston.

"We've used our bullpen up. In our last three games, we've had a six-inning start, [then] 4 1/3 [and] 4 1/3," Gardehire said. "There's just too much pressure on these guys."

The eight-man bullpen is just temporary, though; the team will likely send a reliever, perhaps Thielbar, to the minors in favor of a starting pitcher before Friday's game at Detroit. Hernandez was scheduled to start Friday.

Gibson may be the leading candidate to get called up for his own big-league debut. Gibson (3-5, 3.25 in nine starts for Rochester) pitched a complete-game shutout on Sunday, his second of the season, and Friday would be his next day to pitch. Cole De Vries is scheduled to pitch for the Red Wings tonight and Samuel Deduno is Tuesday's scheduled starter. Both have been rehabbing from injuries. P.J. Walters has also pitched very well lately, though he is not currently on the 40-man roster.

"I like them all. They've all thrown the ball well for us at various times," Gardenhire said. "We haven't had Gibson up at all. He had a good start, but he also had a really bad one before that. We know what Deduno does. Walters has been throwing very well -- there's three options right there. ... I don't have a problem with any of them."

Thielbar is on a flight right now, and is scheduled to arrive in Atlanta about 30 minutes before first pitch. The Twins expect him to be at Turner Field by the middle innings, in time to pitch if he's needed.

Tonight's lineup lacks Oswaldo Arcia and Ryan Doumit, but restores Brian Dozier to the top of the order. Pedro Florimon bats above ninth -- and above Aaron Hicks -- for the first time this year. Kevin Correia is a .116 lifetime hitter.

Tonight's lineups as the Twins try to snap a five-game losing streak:
TWINS
Dozier 2B
Mauer C
Morneau 1B
Willingham LF
Plouffe 3B
Parmelee RF
Florimon SS
Hicks CF
Correia RHP

BRAVES
Andrelton Simmons SS
Jason Heyward RF
Justin Upton LF
Freddie Freeman 1B
Gerald Laird C
Dan Uggla 2B
Juan Francisco 3B
B.J. Upton CF
Julio Teheran RHP