PHOENIX -- Grant Balfour was back throwing Tuesday, five days after arthroscopic surgery on his right knee, then said he'd be surprised if he didn't beat doctor's estimates of a four-to-six week return to pitching.

He threw for about 10 minutes in the outfield at the A's Papago Park facility, then put his body through a two-plus-hour workout afterward that included time on the treadmill and in the weight room. After that, Balfour said "something would be wrong" if he wasn't ready to pitch within four weeks of his original surgery.

He went backward on the treadmill and forward on it up a steep incline, all without evident pain.

It was just last Thursday when Balfour underwent arthroscopic surgery on the meniscus in his right knee. Given a recovery timetable of four-to-six weeks, he was back on his feet within 24 hours and throwing within five days.

"Throwing is not an issue," Balfour said, adding that he wants to keep his arm strong. "The knee feels great."

Manager Bob Melvin was a little more cautious, saying that "it's usually the second day when you start feeling something."

Melvin said he purposefully opted against watching his closer throw on the flat of the outfield grass because he knew Balfour would throw harder than Melvin would want.

The key to the quick recovery is that doctors removed a little bit of meniscus rather than repairing any of it, so less healing is needed.

  • Five more players have
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    connections to a Florida clinic which is at the center of an expanding doping scandal, according to documents obtained by ESPN's "Outside the Lines."

    Players listed in documents from the Biogenesis of America clinic run include A's lefty reliever Jordan Norberto and Padres reliever Fautino De Los Santos, who was with the A's organization for part of the 2012 season.

    A's right-hander Bartolo Colon, who is serving a 50-game suspension including the first five th is season for illegal use of performance-enhancing drugs, also had his name recently pop up as having been a client of the Miami anti-aging clinic that specialized in dispensing PEDs,

    Other players named Tuesday on "Outside the Lines" include Padres shortstop Everth Cabrera, who won the National League stolen base crown last season, and Houston outfielder Fernando Martinez.

  • Rookie pitcher Michael Ynoa is over his bout with the chickenpox and will fly to Arizona from the Dominican Republic Wednesday. The youngest pitcher on the A's 40-man roster, Ynoa, 21, is expected to be on the field Thursday.

  • Second baseman Scott Sizemore was back on the field Tuesday, his second day of full spring workouts. That's one more day than last spring,
    when a leg injury ended his season. "He was able to joke about it, which is good," Melvin said. "You need to have a sense of humor about these things."

  • Melvin continues to be impressed by the work put in by outfielder Michael Taylor, who has a chance to make the club as a backup in the outfield and as a right-handed alternative to left-handed hitting first baseman Brandon Moss. "Michael is working doubly hard," Melvin said. "He's picked up his game."

  • When looked at from behind, infielder Jefry Marte looks like a double for left fielder Yoenis Cespedes. And while he doesn't have Cespedes' power, Marte can muscle up well enough. He hit a few bombs in batting practice Tuesday that were impressive.

  • Melvin has started to call the A's spring training workouts "Camp Versatility." And among the most versatile, he said, is left-handed hitting outfielder Shane Peterson. "His numbers last year told us about him," Melvin said. "But what you see here is that he's a grinder, and he's really strong."