PHOENIX -- Doug Davis made sure his performance earlier in the week was just a bump in the road.
Davis (11-11) won for the sixth time in seven decisions -- his one loss came last Monday, when he lasted a season-low two innings and gave up six runs against Milwaukee. The Diamondbacks remained two games ahead of San Diego in the NL West.
"My control was a lot better and I wasn't falling behind," Davis said. "I was able to get ahead and stay ahead."
"We've got our eye on the scoreboard watching San Diego," Davis said, "so every game is important for us right now."
Davis was less pleased when told Cubs manager Lou Piniella had called him a "crafty" left-hander.
"It's not the first time I've heard it," Davis said. "I'm not thrilled with it. I'd rather be known as a control pitcher."
Ted Lilly (13-7) allowed two runs and four hits over six innings for the Cubs, who maintained a 1½-game lead over the Brewers. Milwaukee lost 6-2 loss in San Francisco.
"As long as we continue to play well we don't have to worry about anything," Piniella said. "If we don't play well, it doesn't matter what anybody else does."
Lilly struck out eight and didn't walk a batter for the third time this season.
The Diamondbacks took the lead in the fourth. Eric Byrnes lined a two-out single to left and Jackson followed with a homer that landed about four rows back in left field.
Jackson's 10th homer was the 23rd allowed by Lilly in 27 starts spanning 168 1/3 innings.
"I think I was a little too concerned with the runner on first base and ended up leaving it out over the plate," Lilly said of his 2-2 fastball to Jackson. "You can only get away with those so many times."
Aramis Ramirez cut the lead to 2-1 in the sixth after Ryan Theriot hit a one-out single and Derrek Lee drew a two-out walk. Ramirez blooped a single to right to score Theriot before Craig Monroe flew out to center to end the inning.
Davis got some help from his defense in the fifth. Matt Murton singled with one out and Jacque Jones hit a sharp grounder toward the right-field hole. But second baseman Orlando Hudson scooped up the ball and spun toward second to begin an inning-ending double play.
The Cubs put runners on first and second against Lyon with two out in the eighth, but the right-hander struck out Monroe looking to end the threat.
"We play a lot of close games," said Arizona manager Bob Melvin. "Our pitchers have to bear down every pitch."
- Eight of Upton's 16 hits have been for extra bases.
- The game was played in front of 46,173, the fourth-largest crowd at Chase Field this season.
- Monroe, acquired by Chicago from Detroit on Thursday, was making his first start for the Cubs.
- Davis has allowed one run or less in six of his 27 starts.
- Cubs pitchers have allowed 10 or fewer hits in a season-best nine straight games, the longest such streak since an 11-game run last September.
- Jackson's home run was his first since a two-homer game Aug. 10 against Washington.