Ken Griffey, Jr. partially tore his patella tendon and partially dislocated his kneecap on Sunday. The injury occurred to his right knee during a rundown in Sunday's game. Griffey, who was already bothered by tendinitis in the knee, will now attempt to recover using a treatment of rest and rehabilitation but could be forced to undergo season-ending surgery if the therapy is not effective.

He has already been placed on the disabled list and will miss a minimum of three weeks and more likely at least six. The initial plan is to immobilize the knee while he begins rehab and then reevaluate his condition in a couple weeks.

Whether he needs surgery before the end of the season or not, this injury will put a serious damper on Griffey's season. You only need to recall Mark McGwire's problems at the plate when he was suffering from his knee problems to view a worst-case scenario for Griffey's abilities when he returns, and McGwire didn't have to worry about playing the outfield.

A key concern is that, while the primary damage may heal, the tendinitis that he struggled with during Spring Training may flair up and cause trouble. Hopefully, the damaged will eventually be fully repaired so that this is not something that bothers him in future seasons.

In Griffey's absence, Ruben Mateo has been called up. Although the team does not care for Juan Encarnacion's fielding skills in centerfield, Encarnacion should receive the majority of the time in center while Griffey is out. Adam Dunn will continue to play left field and is likely to move up to cleanup spot in the batting order. Brady Clark will likely pick up the majority of the newly available at-bats in right field. Considering Mateo is capable of playing center, Reggie Taylor's playing time may actually decrease.

Injuries this season seem to be coming in bunches. Tino Martinez and Mike Piazza are both day-to-day with knee injuries, although compared to Griffey, their problems aren't overly serious. Martinez injured his right knee when he ran into a pole while attempting to catch a foul ball on Sunday. Piazza's left knee was injured in a collision with Chipper Jones at home plate on Saturday. Both have been sidelined with contusions and bruising, but x-rays were negative and they are expected to start Tuesday.

Elsewhere in the NL Central, Moises Alou has yet to play in a game this season and was placed on the DL retroactive to March 31st on Friday. Alou missed most of Spring Training with a strained oblique and then strained his right calf as the season was starting. He's reportedly improving and will be eligible to return from the disabled list April 15th.

The Cubs acquired Mario Encarnacion off waivers from the Rockies Thursday. Encarnacion was subsequently called-up when Alou was placed on the DL. He has both some speed and power but lacks plate discipline.

Roosevelt Brown has taken over in left field during most of the games Alou has missed, with Darren Lewis coming in as a late game defensive replacement. Encarnacion will now share playing time with Lewis.

Although Alou is expected to come off the DL at his first opportunity, I would be surprised if this was his last trip to the disabled list this season. Alou has struggled with this calf in the past and with each season appears to be more and more prone to muscle pulls.

Wiki Gonzalez is the latest player to participate in the trend of hamate bone removal. He fractured the bone in his left wrist during an at-bat on Wednesday. Following the surgery to remove the bone on Thursday, he is expected to miss approximately six weeks. This injury is virtually the same as those suffered by Erubiel Durazo and Luis Matos in late March. Hopefully the rest he will receive while waiting for his wrist to recuperate will allow the strained flexor muscle in his right elbow to heal.

Javier Cardona was called up to assist with catching duties while Gonzalez is on the DL. He will split time behind the plate with Tom Lampkin, though Lampkin will likely see more at-bats as a left-hander and veteran.

Randy Velarde was placed on the DL on Sunday with a fractured left hand retroactive to April 5th. He was hit by a pitch in the A's first game of the season, and his hand was still swollen after several days. X-rays reportedly showed a fracture though it was unclear whether the break was new or a pre-existing problem. While he may be able to return as soon as he is eligible to come of the disabled list, he could be out for up to three weeks.

Mark Ellis was called up to fill Velarde's roster spot. Ellis is a 24-year-old middle infielder who has advanced quickly through the minors after being drafted by the Royals in 1999. He was acquired by Oakland in the three-way trade with Kansas City and Tampa Bay that also brought Johnny Damon to the A's. He has some power and speed and fairly good plate discipline, though his strike zone judgment dipped when he advanced to AAA last season. However, he is likely destined for a bench position as A's prospect Esteban German is still the favorite to take over at 2B full-time sometime in the next two seasons, and Miguel Tejada appears solidly entrenched at SS. Frank Menechino will likely absorb the majority of Velarde's playing time. Ellis will take over as the middle infielder off the bench.