SAN FRANCISCO (AP) — Cincinnati's Johnny Cueto left his Game 1 start against the San Francisco Giants on Saturday night in the first inning because of back spasms.

The Red said he is day to day. The right-hander threw a second strike to No. 2 hitter Marco Scutaro and walked off the mound in obvious pain. A trainer and manager Dusty Baker rushed out to check on him, and the 19-game winner came out moments later.

He retired leadoff man Angel Pagan on a strikeout. During the at-bat, Pagan stepped out of the batter's box and was granted time. Cueto apparently didn't see it and continued his motion.

He threw eight pitches and six strikes for the earliest postseason exit by a starter since Atlanta's John Thomson lasted one-third of an inning in Game 3 of a 2004 NL division series against Houston. Thomson came out with a sore muscle in his left side.

Loading Slideshow...

  • San Francisco Giants center fielder Gregor Blanco can't get to a two-run home run by Cincinnati Reds' Brandon Phillips in the third inning of Game 1 of the National League division baseball series in San Francisco, Saturday, Oct. 6, 2012. (AP Photo/Eric Risberg)

  • The Bay Bridge stands beyond the stadium as fans prepare to watch Game 1 of the National League division baseball series between the San Francisco Giants and the Cincinnati Reds in San Francisco, Saturday, Oct. 6, 2012. (AP Photo/Jeff Chiu)

  • Cincinnati Reds manager Dusty Baker (12) smiles during the introduction of the teams before Game 1 of the National League division baseball series between the Reds and the San Francisco Giants in San Francisco, Saturday, Oct. 6, 2012. Baker is a former Giants manager. (AP Photo/Marcio Jose Sanchez)

  • San Francisco 49ers quarterback Alex Smith, right, is greeted by San Francisco Giants pitcher Sergio Romo after Smith delivered the ceremonial first pitch before Game 1 of the Giants' National League division baseball series against the Cincinnati Reds in San Francisco, Saturday, Oct. 6, 2012. (AP Photo/Eric Risberg)

  • Fans cheer in the first inning of Game 1 of the National League division baseball series between the San Francisco Giants and the Cincinnati Reds in San Francisco, Saturday, Oct. 6, 2012. (AP Photo/Jeff Chiu)

  • Military planes fly over the stadium before Game 1 of the National League division baseball series between the San Francisco Giants and the Cincinnati Reds in San Francisco, Saturday, Oct. 6, 2012. (AP Photo/Jeff Chiu)

  • Cincinnati Reds' Brandon Phillips, right, gets congratulated by Drew Stubbs after Phillips hit a two-run home run in the third inning of Game 1 of the National League division baseball series against the San Francisco Giants in San Francisco, Saturday, Oct. 6, 2012. (AP Photo/Eric Risberg)

  • San Francisco Giants pitcher Matt Cain reacts after giving up a two-run home home to Cincinnati Reds' Brandon Phillips in the third inning of Game 1 of the National League division baseball series in San Francisco, Saturday, Oct. 6, 2012. (AP Photo/Eric Risberg)

  • San Francisco Giants pitcher Matt Cain reacts after giving up a two-run home home to Cincinnati Reds' Brandon Phillips in the third inning of Game 1 of the National League division baseball series in San Francisco, Saturday, Oct. 6, 2012. (AP Photo/Marcio Jose Sanchez)

  • Cincinnati Reds' Jay Bruce heads home on a solo home run in the fourth inning of Game 1 of the National League division baseball series against the San Francisco Giants in San Francisco, Saturday, Oct. 6, 2012. (AP Photo/Marcio Jose Sanchez)

  • Cincinnati Reds' Brandon Phillips swings on a two-run home run in the third inning of Game 1 of the National League division baseball series against the San Francisco Giants in San Francisco, Saturday, Oct. 6, 2012. (AP Photo/Eric Risberg)

  • The fans scramble to catch the two-run home run hit by Cincinnati Reds' Brandon Phillips in the third inning of Game 1 of the National League division baseball series against the San Francisco Giants in San Francisco, Saturday, Oct. 6, 2012. (AP Photo/Eric Risberg)

  • Cincinnati Reds Zack Cozart reacts after being hit by a pitch in the third inning of Game 1 of the National League division baseball series against the San Francisco Giants in San Francisco, Saturday, Oct. 6, 2012. (AP Photo/Eric Risberg)

  • San Francisco Giants center fielder Gregor Blanco can't reach a two-run home run by Cincinnati Reds' Brandon Phillips in the third inning of Game 1 of the National League division baseball series in San Francisco, Saturday, Oct. 6, 2012. (AP Photo/Marcio Jose Sanchez)

  • Cincinnati Reds' Jay Bruce is congratulated after hitting a solo home run in the fourth inning of Game 1 of the National League division baseball series against the San Francisco Giants in San Francisco, Saturday, Oct. 6, 2012. (AP Photo/Jeff Chiu)

  • AT&T Park is seen from McCovey Cove during Game 1 of the National League division baseball series between the San Francisco Giants and the Cincinnati Reds in San Francisco, Saturday, Oct. 6, 2012. (AP Photo/Jeff Chiu)

  • San Francisco Giants' Gregor Blanco steps on the base in the fourth inning of Game 1 of the National League division baseball series against the Cincinnati Reds in San Francisco, Saturday, Oct. 6, 2012. (AP Photo/Eric Risberg)

  • San Francisco Giants' Buster Posey rounds the bases after hitting a solo home run in the sixth inning of Game 1 of the National League division baseball series against the Cincinnati Reds in San Francisco, Saturday, Oct. 6, 2012. (AP Photo/Marcio Jose Sanchez)

  • Cincinnati Reds left fielder Ryan Ludwick makes a diving catch on a ball hit by San Francisco Giants' Brandon Belt in the sixth inning of Game 1 of the National League division baseball series in San Francisco, Saturday, Oct. 6, 2012. (AP Photo/Eric Risberg)

  • San Francisco Giants' Buster Posey hits a solo home run in the sixth inning of Game 1 of the National League division baseball series against the Cincinnati Reds in San Francisco, Saturday, Oct. 6, 2012. (AP Photo/Eric Risberg)

  • San Francisco Giants second baseman Marco Scutaro, left, misses the tag on Cincinnati Reds' Brandon Phillips in the eighth inning of Game 1 of the National League division baseball series in San Francisco, Saturday, Oct. 6, 2012. (AP Photo/Marcio Jose Sanchez)

  • San Francisco Giants' Buster Posey is congratulated after hitting a solo home run in the sixth inning of Game 1 of the National League division baseball series against the Cincinnati Reds in San Francisco, Saturday, Oct. 6, 2012.(AP Photo/Eric Risberg)

  • San Francisco Giants second baseman Marco Scutaro throws to first after missing the tag on Cincinnati Reds' Brandon Phillips, left, in the eighth inning of Game 1 of the National League division baseball series in San Francisco, Saturday, Oct. 6, 2012. Joey Votto was out at first on the play. (AP Photo/Marcio Jose Sanchez)

  • San Francisco Giants' Gregor Blanco strikes out with two men on base in the eighth inning of Game 1 of the National League division baseball series against the Cincinnati Reds in San Francisco, Saturday, Oct. 6, 2012. (AP Photo/Marcio Jose Sanchez)