The right-hander, acquired in a trade with the Detroit Tigers in the offseason, blanked the Los Angeles Angels on one hit through three innings in Arizona's 4-1 victory on Thursday. The right-hander has yet to give up a run in five innings this spring.
"He's got a presence about him on the mound that's easy to like," Diamondbacks manager A.J. Hinch said.
A 95 mph fastball doesn't hurt, either, nor does his upbeat, infectious personality.
"He's an athlete. He's out there to compete," Hinch said. "He loves to pitch. You can tell by his body language, by the way he goes about his business."
Jered Weaver regrouped from a rough first outing for the Angels, allowing one run on three hits and striking out two in three innings.
Los Angeles' lone run came on Mike Napoli's third homer of the spring, off Leo Rosales, Chris Snyder homered for Arizona.
Jackson, an All-Star with the Tigers last year, will start the season as the Diamondbacks' No. 2 starter behind Dan Haren. He breezed through three innings so fast, throwing just 24 pitches, he went to the bullpen to get more work in afterward.
With a strong possibility Webb will start the season on the disabled list as he comes back from shoulder surgery, Jackson is counted on as a big part of Arizona's hopes from a turnaround from its disappointing 2009 season. He won't let any added pressure affect him, he said.
"I mean, the fact that it's there is definitely obvious," he said, "but you can't really go into it putting any more pressure on yourself. You can only do so much as a person, as a pitcher. You can't go out and kill yourself. You just have to do what you're supposed to do anyway, that's pitch deep into games."
Jackson was 13-9 with a 3.62 ERA with the Tigers last season. The Tigers traded him to Arizona for young pitchers Max Scherzer and Daniel Schlereth to Detroit.
Weaver, 16-8 with a 3.75 ERA and four complete games last season, gave up two runs on three hits in 1 2-3 innings his first time out this spring.
"It was a lot better than the last outing," he said after Thursday's appearance. "I was able to locate my off-speed pitch a lot more this time. I was making strides in the right direction."
Tony Abreu had another strong showing in his bid to make Arizona's opening day roster, with a single, double and two runs scored in three at-bats. The infielder is hitting .500 this spring (10 for 20) with seven runs, four RBIs and one strikeout.