The Rockies are in unfamiliar territory. They have a losing streak at Coors Field, the smallest possible one, to be sure, but a reversal, nonetheless, of their recent high-flying form there.

The Chicago Cubs beat the Rockies 6-2 on Friday, meaning the Rockies, who also lost 10-2 to the Cubs on Thursday, must win tonight and Sunday to salvage a split of the four-game series.

The Rockies, who are winless in five games against the Cubs this season, slipped to fourth place, six games behind Arizona. They had not lost consecutive home games since May 30-June 1, when they dropped three straight. Coming off Ubaldo Jimenez's ineffective outing Thursday, the Rockies needed a strong start from Aaron Cook, given the way their rotation lines up. They didn't get it.

Josh Fogg takes the mound tonight. He has been good lately but is the fifth starter - never mind he has become the third starter by default - so the reliability factor is always lurking. And someone, maybe Tim Harikkala, will start Sunday.

Against that backdrop, Cook took the mound in a duel of sinkerballers with Jason Marquis. The latter was very good, leaving after 6 2/3 innings when he beaned Jeff Baker with a 91-mph fastball, knocking Baker's helmet off his head and hitting him in the face. Baker was taken to the hospital for tests.

Ryan Spilborghs was on deck when Baker was hit and at the plate as trainer Keith Dugger tended to Baker.

"He had a cut on his (left) cheekbone," Spilborghs said. "I was probably as scared as he was when he was laying there. Any time you see one of your brothers go down and he can't do anything about it, it's pretty frightening."

When play resumed, Carlos Marmol relieved Marquis, issued a two- out walk to load the bases and struck out Willy Taveras. The Rockies had a better scoring opportunity in the eighth but came away virtually empty after loading the bases with no outs when Bobby Howry relieved Marmol.

Howry got Brad Hawpe to pop out. Troy Tulowitzki's slow grounder to third scored a run, but Howry snuffed out the rally by getting Yorvit Torrealba to fly to center.

Cook suffered his first loss in seven starts dating to July 8. He needed 105 pitches to get through six innings, walked three - he had walked a total of two in 22 innings in his previous three starts - and allowed eight hits.

Cook stranded runners at first and second each of the first two innings and found himself with runners at first and third to start the third, after Jacque Jones' bunt single and first baseman Baker's throwing error. He fielded Derek Lee's hard grounder cleanly and tried to get Jones at second, but he threw far to the left of shortstop Tulowitzki.

Cook took care of Jones himself when he ran him back toward third after fielding a comebacker, and Jones, trying to elude Cook, ran out of the baseline. A walk to Mark DeRosa loaded the bases, and Lee scored on Mike Fontenot's slow grounder to second.

Escaping with one run would have been the best-case scenario for Cook. But he gave up a two-run single to Jason Kendall on an 0-1 pitch.

"I had a great chance to get out of that and pick the guys up," Cook said, "and got a pitch up to Kendall, and he drove it into center field.

"There's a couple other pitches I'd like to have back - the double to Marquis - I know he's a good hitter - and the home run to Jones."

Marquis, with a lifetime .214 average, won a seven-pitch encounter with Cook and began the fourth with a double off the base of the center-field wall. With one out, Jones, who is 7-for-10 with six RBI in the series, fought back from 0-2 to 3-2 and, on Cook's eighth pitch, doubled to left-center.

Tulowitzki doubled home a run with two out in the fourth after Matt Holliday, who led off, was safe on third baseman DeRosa's throwing error.

Cook found a midgame groove and retired six straight batters after intentionally walking Lee after Jones' run-scoring double. That streak ended when Jones, who had two homers in 299 at-bats, drove his third an estimated 442 feet into the second deck in right- center with two out in the sixth.

After Howry rescued the Cubs in the eighth, Matt Murton led off the ninth with a home run against closer Manny Corpas. It was the second home run in two games for Murton and only the fourth off Corpas, who has worked 54 1/3 innings, and the first he has allowed at Coors Field since June 5.

etkinj@RockyMountainNews.com