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Brandon Phillips hit a two-run homer off San Francisco' Matt Cain and the Cincinnati Reds led the Giants 2-0 after three innings of their NL division series opener Saturday night despite losing ace Johnny Cueto to a back injury after eight pitches.

Cueto had the shortest postseason start in the majors in eight years when back spasms forced him to leave while pitching to the second batter of the game. He is day to day.

Reliever Sam LeCure and Game 3 starter Mat Latos held the Giants scoreless as manager Dusty Baker scrambled. The Reds got the lead on Phillips' one-out homer in the third that also scored Drew Stubbs.

Those were the first earned runs Cain has ever allowed in the postseason, ending a run of 23 1-3 straight innings without an earned run that was the fifth-longest ever.

Losing Cueto this early in the series could be a big blow to the Reds. His 2.58 ERA the past two seasons is third best in the majors and Cincinnati now has to rely heavily on its bullpen in the opener of the best-of-five series.

The Reds ran to the NL Central title based on the health of their starting pitchers. None of their five starters got hurt all season and they only needed a sixth starter when Todd Redmond started the back end of a doubleheader in August against the Cubs.

Cueto struck out Angel Pagan to open the game but appeared as if he might have aggravated something when stopping mid-motion when Pagan called time out earlier in the at-bat.

Cueto then pulled up lame on the second pitch to Marco Scutaro and Baker and a trainer rushed out to the mound to check on the 19-game winner, who left the game.

Cueto's outing was the shortest start in the postseason since Atlanta's John Thomson also only retired one Houston batter in Game 3 of the 2004 NLDS. He threw just four pitches before leaving with a sore muscle in his left side.

LeCure relieved and retired the first four batters he faced before loading the bases with two outs in the second. He escaped that jam by getting Cain lined out to right field.

Latos, pitching on three days' rest, came in for the third and worked around a two-out single by Pablo Sandoval.

The Reds are looking for their first postseason win since 1995, having lost seven straight since then in the 1995 MLCS to Atlanta and the division series two years ago to Philadelphia.

After 49ers quarterback Alex Smith one-hopped the ceremonial first pitch to Giants reliever Sergio Romo, Cain picked up where he left off in the 2010 postseason when he didn't allow an earned run in three starts.

Cain pitched a perfect first inning, getting help when first baseman Brandon Belt flipped head over heels over the railing in foul territory to catch a popup from Zack Cozart for the second out. Cain struck out Reds slugger Joey Votto to end the first inning.

Cain pitched around a one-out double to Jay Bruce in the second inning before running into trouble in the third.