One night after Colorado dropped its fourth straight game - having led after seven innings in all of them - the streaking Cubs will seek a two-game sweep in Denver and their seventh straight win overall on Thursday.

Numerous late-inning rallies led the Rockies (9-12) to 21 wins in 22 games last fall as they advanced to their first World Series, but they've been making a habit of squandering leads during their recent struggles.

They had won four straight and led 4-3 in the eighth inning at Houston on Sunday, but reliever Brian Fuentes allowed three runs in the bottom of the eighth inning in a 6-4 loss.

Philadelphia scored five runs in the final two innings Monday, winning 9-5, and Colorado closer Manny Corpas has blown saves the last two days, allowing five runs in two innings. Corpas has blown four of his eight save opportunities.

Aramis Ramirez's two-run home run gave the Cubs (15-6) the lead in the ninth on Wednesday, and Chicago eventually won 7-6 in 10 innings on Ryan Theriot's RBI single.

"It's obviously tough any time you lose leads late," Rockies shortstop Troy Tulowitzki said. "It makes it extra tough. I remember we went through a stretch last year where we did the same kind of thing and ended up all right. At least we know we can still be OK."

Tulowitzki was a bright spot Wednesday, hitting a three-run home run - his first of the season - to put the Rockies ahead. The shortstop had been benched Tuesday, and was dropped to seventh in the order for Wednesday's game due to his .163 average coming in.

While the Rockies have struggled, the Cubs tied Arizona for the league's best record with Wednesday's win - their 10,000th in franchise history. Chicago has won six straight, nine of 10 and 14 of 17, thanks largely to the league's highest-scoring offense.

The Cubs lead the majors with 133 runs. They've scored at least seven in each of the last five games, totaling 48 runs over that span. Ramirez is 9-for-18 with three home runs and nine RBIs in those games.

"I don't think we could predict the way we were going to be swinging the bats right now," Cubs closer Kerry Wood said. "I don't think we have more than one guy in the lineup hitting under .300."

Jason Marquis will hope to again benefit Thursday. Marquis (1-0, 3.86 ERA) got 11 runs of support last Saturday, allowing just one run in six innings of a 13-1 win against Pittsburgh.

Marquis has never lost at Coors Field, winning all three of his starts, and allowing only four earned runs in 19 2-3 innings. Last August, he yielded an unearned run and five hits in 6 2-3 innings of a 6-2 victory.

The Rockies will look to Aaron Cook to end their skid. Cook (2-1, 3.12) has pitched well this year after missing more than two months late last season with an oblique injury.

He's allowed just five earned runs in 20 innings in his last three starts, going 2-0 over that span. In his only home start, he yielded just two hits in seven innings of a 2-1 win over Atlanta, and he gave up just four hits in seven innings at Houston Saturday in the Rockies' last win.

"Aaron's last four innings were great," Colorado manager Clint Hurdle said. "They got four hits on him and in this park that's just a dominating effort."

The Rockies are trying to avoid their second five-game losing streak of the season, while the Cubs are looking to win seven in a row for the first time since last June.