Boston Red Sox catcher Jason Varitek knows what fellow catcher Doug Mirabelli goes through on a regular basis. Varitek is Boston's primary catcher, the guy who goes out there day after day after day.

Mirabelli's primary task is serving as knuckle-ball pitcher Tim Wakefield's catcher. A knuckle ball is unlike anything else. Varitek has tried catching Wakefield's pitches as they flutter and dart and zoom their way toward home.

"The best way to explain it is you're sitting there with this thing coming at you," Varitek said. "It can go north, south, east or west. And any combination of them. A little southeast. A little southwest. It could break a little northeast. It could go straight.

"It could do any of the above and you're not quite sure what it's going to do and you're just at its disposal."

Mirabelli knows from the stands or the press box or television, all those unexpected breaks aren't as apparent or challenging.

"It's nerve-wracking," Mirabelli said in the locker room at the Red Sox training facility in Fort Myers. "First of all, you don't want to look like an idiot."

Mirabelli is not an idiot. He's a 34-year-old veteran about to begin his fifth season with the Red Sox. The starting job belongs to Varitek. Mirabelli understands that.

Mirabelli, who hit .281 with nine homers and 32 RBI in 59 games last year, could have left the Red Sox as a free agent. He chose to stay, even with the starting job belonging to Varitek.

"It just came down to what was best for my family and my comfort level because I've loved it here ever since I got here," Mirabelli said. "It came down to being a pretty easy choice for me."

The Red Sox appreciate having a second catcher of Mirabelli's ability and stability. Varitek was asked the other day about having Mirabelli around "to spell him." Varitek thought the question was unfair to Mirabelli.

"He's a great player," Varitek said. "I don't ever look at it as he's spelling me. I look at him as an equal. ... I just can't say enough about him, how happy I have a chance to play with him longer."

Wakefield also values Mirabelli's work.

"It's the same comfort level the other guys have with Jason," Wakefield said. "He catches me every day. He knows my little idiosyncrasies, can correct things when things are going bad. He gives me a lot of confidence back there."

Ever since Red Sox manager Terry Francona arrived in town, he's responded to questions about Varitek by pointing out the team has two catchers.

"What he did last year was remarkable," Francona said. "Offensively, he gave us lifts when we needed lifts. When he'd catch Wake he seemed like he'd hit home runs. When (Varitek) was out with a suspension, we won those games. ... He's a valuable member of our club and he has a good influence on the other guys."

It's a challenging job for two reasons. One is catching Wakefield. The other is being a part-time player, a role that Mirabelli has accepted.

"It's not an easy thing to do," Mirabelli said. "I love the job. It's not necessarily one that if you had your choice you'd be in my situation. I've grown into it."