PHOENIX -- Dontrelle Willis is back in the National League. He brought his command problems, his bat, and his relentless competitiveness with him.
The latter is a trait the Arizona Diamondbacks sorely can use.
Willis pitched six scoreless innings and scored a run on a headfirst slide in his Arizona debut on Saturday night and the Diamondbacks held on for a 4-3 victory over the Colorado Rockies.
"So far, so good," he said.
The big left-hander, acquired Tuesday from Detroit, gave up five hits, walked four and hit a batter, but the Rockies were 0-for-10 against him with runners in scoring position. When the Rockies hit the ball hard, and they did a number of times, it was either right at a defender or someone made a standout defensive play.
"They definitely have a lot of talent," Willis said of his new teammates. "I think the more they believe in themselves and believe in me, the better the results will be."
Willis (1-0) allowed five hits and struck out three.
"You talk about a guy that loves to play the game, what a joy to watch," Arizona manager A.J. Hinch said. "With all his imperfections and how much he battles himself, to watch a guy go out on the field and compete and lay it all on the line is a good site to see."
Ryan Roberts, star of Friday night's come-from-behind 7-6 victory over the Rockies, drove in two with a two-out, pinch-hit double in the sixth as Arizona won its second in a row after losing 10 straight. Sandwiched around an 0-9 road trip, the Diamondbacks have won six of seven at home.
Arizona tied a franchise record with its sixth straight one-run game.
The Diamondbacks can complete a three-game sweep on Sunday, but they will have to do it against Ubaldo Jimenez (10-1).
"We're not playing the right way," Colorado's Carlos Gonzalez said. "Yesterday we struck out like 14 times. We could have won the game but we played so badly they came back and won. Today Dontrelle he pitched a really good game, but I think we need to get better in about everything."
Jhoulys Chacin (3-4) struck out nine, the most in his 17 big-league appearances, eight as a starter. He held Arizona to an unearned run through five but surrendered three in the sixth, two on the double by Roberts, whose pinch-hit single in the ninth won the game for the Diamondbacks on Friday.
Colorado scored three in the seventh. The Rockies loaded the bases with no outs against reliever Carlos Rosa, then got sacrifice flies from Troy Tulowitzki and Brad Hawpe. Colorado loaded them again on Melvin Mora's single and a walk to Chris Iannetta.
With the crowd booing another weak Arizona bullpen effort, Aaron Heilman relieved Rosa and walked pinch hitter Seth Smith on four pitches to bring in the third run of the inning. Heilman struck out pinch hitter Ian Stewart to end the inning, then retired the side in order in the eighth.
"The unfortunate thing is the game boils down to this -- 0 for 11 with runners in scoring position," Rockies manager Jim Tracy said, "and we left 12 runners on base. There's very little else to day. ... The opportunity was there. We just couldn't capitalize."
Willis, one of the best hitting pitchers in baseball but with just three at-bats in three seasons in Detroit, singled to lead off the third. Johnson followed with what should have been a double-play bouncer to first, but Jason Giambi threw over the head of Tulowitzki covering second and both runners were safe. Willis scored from second on Stephen Drew's single to left, sliding head first and brushing his pitching hand across the plate.
Willis acknowledged that the slide was "not ideal" from a manager's perspective, although he's done it "a bunch of times."
"I don't know how to slide feet first," he said. "I'm going to have to work on that."
Giambi got the start because Rockies manager Jim Tracy has given 1B Todd Helton Saturday and Sunday off. Tracy said Helton, mired in a 2-for-23 slump, will be moved down in the batting order from the No. 3 spot when he returns. ... Colorado matched its season-long losing streak of three. ... The Diamondbacks' Justin Upton fanned three times to continue to lead the majors with 76 strikeouts, two more than teammate Mark Reynolds, who struck out twice. .... The Diamondbacks' Chris Young stole three bases, a career best.