CINCINNATI -- Scott Rolen will not play during this weekend's series against Houston, Reds manager Dusty Baker confirmed Saturday. Rolen had told MLB.com that he has a protrusion in two discs in his lower back which were revealed by a MRI conducted Wednesday.

"He'll at least be out this weekend," said Baker. "We'll just do what we need to do in the meantime."

Despite playing without Rolen, a 37-year old veteran and important clubhouse presence who has batted .314 since the All-Star break even with the nagging back issues, the Reds have a viable option at third base in NL Rookie of the Year candidate Todd Frazier.

Frazier is hitting .356 in his past 28 games and has reached base in 29 straight games.

Cozart out with oblique strain, back 'next week'

CINCINNATI -- Reds shortstop Zack Cozart was in no mood to talk to reporters on Friday after testing his sore back with stretching and fielding grounders. A MRI performed Friday revealed the underlying source of Cozart's frustration: a left oblique strain.

Cozart's stellar play with both his bat and glove has earned him National League Rookie of the Year consideration. But an oblique strain will require additional rest for Cozart, and more lineup shuffling for Reds manager Dusty Baker.

"Best scenario, sometime next week," said Baker, when asked about a timetable on Cozart's return. "I'd rather have it [be] now than the last week of the season. Hopefully he'll be ready. I hope everybody's ready. We're in the final stretch now."

Cozart, who first experienced pain in the middle of his back on Tuesday, is batting .243 with 32 doubles, 15 homers and 32 RBIs.

On Saturday, Wilson Valdez made his third start at shortstop in the past four games. Rookie Didi Gregorious had the other start. "We just have to mix and match, again," said Baker.

Cozart was receiving treatment prior to Saturday's game and wasn't available for comment.

Blown save ends streak for Chapman at 27

CINCINNATI -- Aroldis Chapman has been so good this season that on the rare occasion when he blows a save, it's big news.

Chapman allowed a three-run home run to Matt Dominguez in the bottom of the ninth inning on Friday as Houston rallied for a 5-3 victory. It was Chapman's first blown save since June 24, snapping a streak of 27 straight.

Reds manager Dusty Baker said Chapman will be available to pitch again on Saturday. Baker likes to get his closers back on the mound soon after a rough outing. "I always try to," Baker said. "I'll take 27 more (straight saves) until the next one. Consider how good he's been in his first season of closing, not even a full season."

It was just the second career homer for Dominquez, a 23-year old rookie. "That's September baseball," said Baker. "There's always some kid that hurts you in September. Hopefully some of our kids can do that."

After Friday's outing Chapman's ERA against National League teams "rose" to 0.73. NL opponents are hitting just .128 against him.

Worth noting

• Three Reds rookies had their uniform numbers changed prior to Saturday's game: Shortstop Didi Gregorious from No. 68 to No. 36; infielder Henry Rodriguez from No. 67 to No. 25; left-hander Tony Cingrani from No. 70 to No. 52.

• In 16 series completed since the All-Star break, the Reds are 11-3-2 with five series sweeps.