PHOENIX -- The D-backs know they have a potent one-two punch at the top of their rotation in Zac Gallen and Merrill Kelly to go along with steady veteran Zach Davies, who recently returned from a stint on the injured list.

For the D-backs to go where they want to go this year, though, they will need their younger starting pitchers to step up and fill in the final two spots.

That’s why the continued improvement of left-hander Tommy Henry is so important and why his dominating outing against the Rockies in which he allowed just two hits over seven innings in Arizona’s 6-0 win Wednesday night was such a welcome sight.

“Obviously, we need Merrill and Gallen to pitch well for us,” D-backs pitching coach Brent Strom said before the game. “They’re the two mainstays that are both All-Star candidates. So I just knock on wood that our young starters can start to get us into the sixth and move forward from there. If we're going to be successful, they're going to have to step up.”

Henry sure did Wednesday, turning in his finest outing in his 17th big league game (16th start).

“Everything was working off of Tommy tonight,” D-backs manager Torey Lovullo said. “It was a great outing for him. He just filled the strike zone, had a ton of swing and miss with the secondary stuff and followed a great game plan.”

Henry was efficient with his pitches as well, throwing just 46 through the first four innings, allowing just one hit and a walk over that stretch.

The quick innings on defense allowed the D-backs’ hitters to get back on the attack, and they put an early stranglehold on the game by scoring three runs in the first inning and two in the second.

“It seems like we can just get into a rhythm,” said outfielder Jake McCarthy, who reached base three times. “When everything's working, I just think we all sort of feed off of it. It's nice to see it coming together [for him]. It seems like all of his pitches are working and he's being accurate with where he wants to throw in certain situations. So it was awesome tonight to see him go out and just sort of dominate, and I just think he's going to continue to get better.”

Henry’s routine was thrown off prior to this start as the D-backs shuffled their rotation a bit.

Henry’s last start came on May 22 in Philadelphia, where he allowed two runs over 5 2/3 innings.

With Davies returning from injury and on a limited pitch count on Saturday, the D-backs used Henry in relief and he threw 1 1/3 scoreless innings.

“It was just kind of a different week in terms of routine,” Henry said. “Overall, I think it was one of those things where you’ve just got to kind of stay ready, do what you can to make it as normal as possible, but at the same time embrace the fact that it's not normal.”

Henry isn’t going to overpower hitters with his fastball, so locating it is important. His changeup is now a real weapon for him. It’s a pitch he has worked hard at with Strom.

The two have also worked a lot on his mechanics recently, which has helped all of Henry’s pitches, but especially the change.

“It's been feeling pretty good as of late,” Henry said. “I feel like the command of it, I'm able to command it in the bottom part of the zone more consistently, which is the biggest part of a changeup. Swings and misses are nice, but you kind of want action on it. You want the ground ball, you want the double play, you want something to get back into counts. And so it's kind of become a pitch that I can use in those situations.”