TUCSON, Ariz. -- Randy Johnson felt so good during his bullpen session on Thursday that he threw seven pitches more than scheduled.

It was the third bullpen session this spring for Johnson, who is attempting to come back from surgery on his back last October. The left-hander worked out of both the windup and stretch as he threw 52 pitches, all fastballs.

"I thought things went pretty well," Johnson said. "I'm progressing."

Johnson threw 25 pitches his first time on the mound last week and followed that up with 37 on Monday. He initially was going to throw 45 on Thursday, but when he reached that point and still felt good, he kept going until he "hit the wall."

"I'll throw again on Sunday," Johnson said. "Probably about the same amount of pitches that I threw today, simply because I was only supposed to throw 45 today. I might try to start throwing a few breaking balls and things like that now that I'm feeling a little more comfortable."

The D-backs will re-evaluate Johnson after Sunday's session and then plan out his next couple of sessions. Unless there is some radical change, Johnson will begin the season on the disabled list, but it's far too early to say when he would be able to return.

Johnson said after his next bullpen session or two he will be at the point he usually is when he reports to Spring Training.

"The projected target date [given by the doctor] was in May," Johnson said. "I'd still like to think that some time in April. When? I don't know, but I think I'm taking the appropriate steps and everything is kind of coming along. Today was progress in the sense that I threw 10 more pitches than I was supposed to. So to pinpoint a date that I'm going to pitch is kind of premature at this point when I'm just throwing bullpen sessions right now."

The next step for Johnson after he has worked up his pitch count a little more in bullpen sessions is to face hitters for the first time.

"As soon as I feel like I've got my legs under me, hopefully the middle of next week, we'll be at about five or six bullpen sessions at that point, hopefully everybody, myself included, will feel comfortable with where I'm at and we'll grab a couple of volunteers and I can throw BP," he said.

Even when completely healthy, Johnson has never put up big numbers during Spring Training. Instead he spends the time working on his pitches and building stamina.

"I've never been worried about my Spring Training stats, and this year will be really no different than that," Johnson said. "I will evaluate my starts on how I feel and how I feel the next day and the amount of pitches I throw each inning and the quality of them. By no means am I worried. If I get wracked around, everyone will say, 'Well, it's because he's older or his back is bad.' But I got wracked around four consecutive years and I rattled off four consecutive Cy Youngs.

"I'm not trying to make the team here is what I'm trying to say. All I'm trying to do is make progress every day and get my legs under me and feel confident and comfortable."