Updated

Rookie left-hander Brooks Raley makes the fourth start of his career Saturday when the Chicago Cubs take on the visiting Colorado Rockies in game two of a three-game weekend series at Wrigley Field.

Raley, a 24-year-old from San Antonio, Texas, was a sixth-round pick of the Cubs in 2009 and was 22-27 across three levels of minor-league play while posting a 3.74 earned run average in 414 innings.

He made his big-league debut on Aug. 7 and was hit hard - seven runs on eight hits in four innings - by the San Diego Padres, then allowed three runs in six innings of a loss to Cincinnati five days later.

He broke through for victory No. 1 in start No. 3, when he allowed three earned runs on five hits in 5 1/3 innings of Chicago's 9-7 defeat of the Reds at Great American Ball Park on Aug. 18.

In 15 1/3 composite innings, he's struck out 10 batters and allowed an overall .281 batting average.

He's countered by Colorado youngster Alex White, who looks for win No. 6 in career start No. 26.

The former first-round pick of the Cleveland Indians was dealt to Colorado in the trade that sent former Rockies ace Ubaldo Jimenez to Ohio.

White was 2-4 in seven starts with the Rockies at the tail end of 2011 and was 2-3 this year after defeating the Los Angeles Dodgers on June 3, but he's since gone 0-3 in nine starts.

He's lasted no more than four innings in his last four outings while picking up a string of no-decisions - combining to allow 14 hits and six runs in 16 innings with 12 strikeouts.

White has never faced the Cubs.

On Friday, Colorado starter Drew Pomeranz was in line for his first win since July 6, but the Cubs rallied for three runs in the eighth inning to win the opener, 5-3.

Brett Jackson crushed a game-tying home run and Joe Mather delivered a go- ahead single to earn the Cubs their fifth win in their last 23 games.

Pomeranz picked up a no-decision after holding the Cubs to two runs on two hits in five innings. He struck out one and walked one as he has now gone eight starts without a victory.

Carlos Gonzalez slammed his 21st home run, but the Rockies saw their five-game win streak come to an end.

"It's a tough loss, but we can't let that affect us," Gonzalez said. "We've been doing a great job. We just need to continue the way we've been playing."

Jackson crushed a no-doubt solo shot to right field off Matt Belisle (3-5), just the Cubs' third hit of the afternoon, to tie the game at three in the eighth inning.

"It was very nice to get that first Wrigley homer," Jackson said.

The teams last met in 2011, when the Rockies won the season series, 4-2. The Cubs last won the series in 2008.