TUCSON, Ariz. -- These were only two innings in a "B" game, but Randy Johnson looked a lot like the Big Unit again.

Returning to Arizona and coming off of back surgery, Johnson had his first game action of the spring on Saturday. Pitching against a group of Chicago White Sox, most of whom had Major League experience, Johnson was sharp.

He retired six of the seven batters he faced, striking out three and giving up only an opposite-field double. He threw 32 pitches, 19 for strikes, and recorded first-pitch strikes to six of seven batters. His fastball was clocked as high as 94 mph.

But his performance was probably even more encouraging than the numbers indicated. His slider had the familiar bite to it. His pitches commanded both sides of the plate. He had remarkable command, particularly for someone who was making his first Spring Training appearance in a game setting.

Johnson was understandably happy with his work. "It's kind hard to work on things when you're between the lines. You're competitive, and you don't want to go out there and pitch poorly," he said. "I'm very pleased with where my slider's at right now. To me, at this juncture, only going out there and being competitive one time, I think I'm ahead of schedule on that. As far as my command, I'm ahead on that. But everything is predicated on how I feel tomorrow and how effective I am five days from now."

What does "ahead of schedule" mean to a pitcher who is coming back from back surgery, but is also headed for the Hall of Fame?

"I'm ahead of schedule, as far as, I mean, I didn't kill anybody, I didn't walk a boatload of batters," Johnson said. "So it was a pleasant surprise. I'm ahead of schedule as far as I don't feel I have to make up a lot of ground in order to get to where I need to be. It's nice to know that's where I'm at right now, that's where I can be, and I mean to build off that. If I went out there and didn't pitch well, then I would realize I had a lot of work to do."

Johnson had thrown five bullpen sessions and two batting practice sessions before this, but there can be no substitute for an actual game. "The only time you really know [where you're at] is throwing in a game against different hitters," Johnson said. "Today was that day. I've got a long ways to go; stamina, endurance, innings, pitch count, all that. But it was nice to know that I walked away unscathed in two innings and felt like I was in command, against some Major League hitters, too.

"If I can keep that quality and add quantity, then absolutely, I would be where I need to be at."

Diamondbacks manager Bob Melvin was more than a little pleased by Johnson's performance, as well.

"For me, the most impressive thing was his command," Melvin said. "A lot of times, the first time out, you can get a little out of whack mechanically, especially power pitchers. That inside part of the plate is pretty important to him. You fly open just a little bit, you don't get it there. Every time he'd leave one out just a little bit, he'd make the adjustment on the next pitch. The velocities kept climbing as the outing went along. And he had a very good slider, both a strike slider and a down-and-in slider. So I don't know that it could have gone any better than it did for the first time against hitters.

"He commanded both sides of the plate and he hit 94 [mph]. Not that that's something we were looking for, but typically in your outings early in these games, your velocity can be four, five, six miles per hour less. Obviously, we don't expect it to be 100 [mph], but to see him touch 94 like that the first time out was pretty impressive."

Johnson will now go on a five-day rotation schedule, gradually building up his innings. He will likely pitch against the Padres in an exhibition game at Chase Field on Thursday. The Diamondbacks are hopeful that he can return to the rotation by mid- to late April.

"We certainly haven't hit any roadblocks yet," Melvin said. "Everything's gone fairly smoothly. We've kind of erred on the side of caution as far as giving him a couple of extra days. But right now we expect to be on that five-day schedule."

Johnson isn't mentioning any date later than April for his return, either.

"This was my first [game], so, say what you will, I'm a little behind," he said. "But I'm pretty sure it won't be May or June when I'm back pitching for real either. Where it could be for a lot of other people, it won't be for me."

Johnson's performance on Saturday was an extremely encouraging sign for the Diamondbacks. This is a talented but relatively young team. If Johnson could be plugged into the rotation and pitch with anything resembling his historical effectiveness, he and 2006 NL Cy Young Award winner Brandon Webb would form a truly imposing duo at the top of the Arizona rotation. As Melvin suggests, given Johnson's stature in the game, his presence on the mound, pitching the way he has been known to pitch, could be a major boost for this club.

"Psychologically, he's very important to our club, too," Melvin said. "One of the things we've tried to do is upgrade our rotation; the quality and the number of innings that these guys pitched, we have four guys who have pitched 200 innings and all four pitched Opening Day last year.

"With a young, inexperienced club out on the field as far as position players, we really have a lot of experience in the starting rotation. For me, the psychological effect of running out a starter that gives your club a chance to win every day is the key psychological advantage each and every day."

That was the definition of Johnson in the prime of his career, including the six years he spent with the Diamondbacks. Returning from two years with the Yankees, which were not the peak times of his career, coming off of offseason back surgery, questions will linger about how much of his best form can be regained, particularly at age 43.

A "B" game on a back field at Tucson Electric Park is some distance from the big time. But for Johnson and the Arizona Diamondbacks, all the signs at the beginning of his return trip were extremely encouraging.