Jackson tries to win a career high-tying fourth straight start when he takes the mound against the Colorado Rockies, who have hit him especially hard over the course of his career.
After a rough first three months, Jackson (6-10, 5.11 ERA) seemingly found his form in his final three starts before the All-Star break. The right-hander won each outing while posting a 1.93 ERA and holding opponents to a .203 average - significantly lower than his season mark of .271.
"This is probably the craziest start I've had in baseball," he said of his first-half efforts. "It's a game of grinding it out. As long as you believe and you have the confidence that you can come in and turn things around, it's all that matters.
"Nobody expected me to start like I did - myself, the front office, the team, the managers. No one. But it's a game, you have to keep grinding. You can either sink or you can swim."
Jackson pitched seven innings of three-hit ball to beat St. Louis 3-0 on July 11.
"He was really sharp against the best offense in baseball," manager Dale Sveum told MLB's official website. "He had a lot more conviction with his pitches, and wasn't worried about pitching as much as throwing."
Jackson won four consecutive starts July 25-Aug. 10, 2008, while with Tampa Bay.
Despite his hot streak, Jackson may not be looking forward to facing the Rockies (47-51). He's 1-2 with a 15.12 ERA in seven career matchups with Colorado - by far his highest mark against any team.
Jackson has surrendered 18 runs in 5 1-3 innings during his last two starts in Colorado. Troy Tulowitzki, Carlos Gonzalez, Dexter Fowler and Michael Cuddyer are a combined 17 for 26 (.654) with a home run, three doubles and two triples in their matchups.
Colorado gives the ball to Tyler Chatwood (5-3, 2.56), who has yielded two or fewer runs in all but one of his last 11 starts. The right-hander recorded his first career complete game in a hard-luck 1-0 road loss to the Los Angeles Dodgers last Saturday.
"We didn't get a win, but I don't think his outing was wasted," Cuddyer said of Chatwood, who has never faced the Cubs. "I think he can continue to build off that."
After dropping Friday's opener 3-1, the Rockies bounced back Saturday with a 9-3 win. Gonzalez hit his NL-leading 26th homer and Fowler went 2 for 3 with a season high-tying three RBIs.
"I have a lot of confidence in our offense. I know we've struggled but it's a good offensive club and I stick by that," said manager Walt Weiss, whose team has gone 12-21 since a 7-3 stretch last month.
Colorado improved to 20-7 at home when Gonzalez drives in at least one run. He is batting .384 with eight homers, 17 RBIs and 19 runs in 22 career games against Chicago (43-52).
The Rockies have hit .350 in taking 11 of 13 home matchups in the series, a stretch in which they've outscored the Cubs 103-53.
Colorado placed closer Rafael Betancourt on the 15-day disabled list after he had his appendix removed Friday. Rex Brothers is expected to handle ninth-inning duties with Betancourt sidelined.