WASHINGTON -- The Washington Nationals had a decision to make before hosting the Cincinnati Reds in the series finale on Sunday at Nationals Park.

And the Nationals were in the situation of having to choose between using unbeaten pitcher Stephen Strasburg (10-0, 2.90) or top pitching prospect Lucas Giolito (0-0, 0.00) to start against the last-place Reds.

That is a choice that many teams wish they had to make.

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"It's not up to me, it's up to how Strasburg feels," manager Dusty Baker before Saturday's game. "Right now he's feeling pretty good, but the decision will probably be made tomorrow. It might be a gametime decision."

After the game, Baker said: "We're getting one of our main men Stras back tomorrow. He can put us back in sync for the remainder of the first half."

Strasburg, the No. 1 overall pick in the 2009 draft, went on the disabled list June 26, retroactive to June 16, with an upper back strain. If he comes off the DL to pitch Sunday, the Nationals will have to make a roster move.

His place in the rotation was filled on Tuesday by Giolito, another former first-round pick who went four innings and allowed just one hit against the New York Mets in a rain-shortened outing.

It was the first big league appearance for Giolito, considered the top pitching prospect in the minors this year.

The big right-hander from Los Angeles had never pitched above Double-A Harrisburg before he was called up to start against the Mets. One scenario would be for the Nationals to send Giolito to Triple-A Syracuse, then call him back up later in the year.

"On any given night, he has three well-above-average pitches working for him," Mark Scialabba, the director of player development for the Nationals, said of Giolito. "Along with his fastball and curve, which are well documented, his changeup has become a weapon he can use against both left- and right-handed hitters. He's a tremendous student of the game and is striving to become a complete pitcher with the ability to field his position and hold runners well."

The Nationals and general manager Mike Rizzo are not hesitant to dip into their minor league system to aid the 25-man roster.

Last June, right-hander Joe Ross -- who started against the Reds on Saturday night -- was summoned from Double-A Harrisburg to join the rotation. He was later sent back to Triple-A Syracuse, then was called back up to Washington to end the season.

The Reds will send lefty John Lamb (1-4, 4.60) to the mound on Sunday. He has never faced the Nationals.

Cincinnati has begun an 11-day, 10-game road trip in rough fashion after a 13-4 loss Thursday and then a 4-3 loss in 14 innings on Friday. They came through with a 9-4 win in 10 innings late Saturday. It was the first extra-inning loss at home for Washington after nine such wins over the past two years.

The Reds were 7-2 against the Nationals over the last two series before the four-game series began here Thursday.

Manager Bryan Price had to juggle his lineup on Saturday.

He dropped second baseman Brandon Phillips to the No. 6 spot in the order against Washington.

"It's just trying to get him back to where he is really feeling comfortable at the plate," Price said of Phillips.

Joey Votto was a late scratch from the lineup just before the game with a sore right shoulder. Price said he is day-to-day. The injury came in Friday's game when Votto dove into second on a double.