PHOENIX (AP) -- John Jaso took the field with the rest of his Oakland Athletics teammates for their first full-squad workout of spring training on Thursday.
He'd already taken a ball off his mask in spring training, an important hurdle for him to clear in his return to baseball.
Jaso is coming back from a concussion that ultimately knocked him out for almost half of last season. A foul tip that struck him in his mask in a game on July 24 led to headaches, dizziness and nausea for some time, and he never got cleared to play.
''I've had a few concussions in the past but nothing this extreme. I almost blacked out on the field out there,'' Jaso recalled. ''It was pretty intense. The other concussions I had were just feeling dizzy and stuff like that.''
Jaso since been given the go-ahead by renowned concussion specialist Dr. Micky Collins, and is back to work in full.
The concussion affected Jaso's depth perception and his ability to pick up objects flashing into his line of sight, so Jaso got vision tests from Dr. Collins when he met with him in Pittsburgh before the start of spring training.
Until then, Jaso admitted feeling concerned.
''I'd say the most scary part about it was if I was to do the tests again and they showed the same results, would it be the end of my career if I took another few foul balls, couple of more wacks to the dome?'' Jaso said.
Jaso, 30, was the A's opening day catcher last season. He homered in the same game in which he was injured, and batted .271 with 21 runs batted in before the concussion.
He wants to continue to catch, even though the A's could use him at first base or as a designated hitter at times. Manager Bob Melvin likes versatility in his players and said the team's two other catchers who have seen the most action the past two seasons, Stephen Vogt and Derek Norris, could be asked to play other positions as well.
''I know he's using a heavier mask now and trying to combat the impact. But you never really know until you get back there and take few off there,'' Melvin said. ''I know he's excited about being cleared for all activity. He wants to catch and he wants to be part of the pitching staff and not just a one-way player.''
It's also no guarantee that Melvin decides to keep three catchers on the major-league roster when the season starts.
Jaso isn't thinking in terms of having to win back his starting job, and even though he wants to catch, is willing to play elsewhere just to get back on the field.
''I just have to come out and do what I do,'' Jaso said. ''I don't feel where if I have to come out and win something and I don't get it, it's a huge disappointment. I've already won just being here. Everything else is just icing on the cake.''
NOTES: Melvin's message to the team prior to Thursday's workout was similar to the past two seasons. He talked about staying focused on ''what we need to do and not get caught up in any expectations anywhere other than the expectations we have for ourselves.'' ... The clubhouse, in typical A's fashion, was loose and abuzz with activity just before the workout. Rap music blared just before Melvin's speech to the team. ''We have a lot of fun,'' Melvin said. ''You're with each other for the better part of eight months. We have good leadership led by a guy like Coco (Crisp), who we re-signed. He monitors the clubhouse very well.'' ... Utility infielder Alberto Callaspo will be eased into playing first base, Melvin said. The A's hope to get Callaspo some at-bats against left-handed pitching with Callaspo playing first in spring training.