DENVER (AP) — The Colorado Rockies have already dealt with plenty of injuries to their starting staff. They added another to the list Tuesday night.
Brett Anderson cruised through three innings before back spasms ended his night, and the Colorado bullpen struggled again in a 6-5, 12-inning loss to the Chicago Cubs.
Nolan Arenado homered and Boone Logan (2-2) took the loss for the Rockies, who have dropped five straight.
Lefty Anderson has been pitching well after missing two months with a fractured finger on his pitching hand. He allowed just one hit and led the game 2-0 Tuesday but left after one pitch in the fourth due when his back began to seize.
"His back locked up and it doesn't look too good now," manager Walt Weiss said. "We've had more of share of injured pitchers this year. We are going down that road again."
Javier Baez homered in the 12th inning in his major league debut to lead the Cubs to the win.
Wellington Castillo also homered for the Cubs, who have won four of five.
Baez, a prized prospect called up before the game, struck out in three of his first five at-bats before hitting Logan's first pitch of the 12th an estimated 414 feet into the Rockies' bullpen.
Hector Rondon (3-3) blew his fourth save but got the win and Carlos Villanueva picked up his second save.
Franklin Morales came on for Anderson and threw two scoreless innings before Castillo led off the sixth with his eighth home run of the season to cut Colorado's lead to 3-1.
The shaky Colorado bullpen faltered in the seventh. Three relievers combined to walk six batters in the inning, three of which scored to give the Cubs a 4-3 lead.
Arenado tied it in the bottom of the seventh with his 10th home run of the season.
"The game was lost in the sixth and seventh innings," Weiss said. "We had a chance to add to our lead in the sixth and didn't. And the seventh with all the walks."
The Cubs took a 5-4 lead in the top of the 11th but Charlie Culberson tied with a two-out single off Rondon in the bottom of the frame.
"I faced him in Chicago and he got me," Culberson said. "I knew what he had and made an adjustment. I relaxed and got a good hit to pitch."
The Rockies took a 2-0 lead in the second on Brandon Barnes' two-run double over the bag at third base.
Colorado added another run on a walk and three hits in the fifth inning.
Anderson's outing was the 20th consecutive start by a left-hander for Colorado. Only the 1982 Kansas City Royals have started consecutive lefthanders for 20 straight games in the last 100 years. The streak will end with right-hander Jordan Lyles scheduled to start Wednesday's game.
Cubs: Right-handed reliever Kyuji Fujikawa is with the team and close to returning after missing more than a year following Tommy John surgery. In 12 rehab outings this year Fujikawa has a 0.77 ERA and 13 strikeouts in 11 2-3 innings. He last pitched in a major league game on May 26, 2013.
Rockies: Shortstop Troy Tulowitzki is eligible to come off the disabled list Wednesday but hasn't started baseball related activities. The leading hitter in the major leagues has been out since suffering a left hip flexor strain in Washington on July 19 and Weiss said Tulowitzki could return in the next week.
Cubs: Jake Arrieta (6-2, 2.11) will try to duplicate his strong start last week when didn't allow a Rockies' baserunner until late into the fifth inning in the Cubs' win at Wrigley Field. The righty allowed just three hits in seven innings of work but faces a stiffer challenge at Coors Field.
Rockies: Lyles (5-1, 3.52) will return to the rotation after missing two months with a fractured left hand. Lyles, acquired in an offseason trade with Houston, was pitching effectively before suffering the injury on a comebacker against Arizona on June 4.