Bill Mueller found out on Friday that an MRI had revealed more damage in his right knee. He will have his third procedure on that knee since May 28, 2004, today in Phoenix, to be performed by Dr. David Zeman. Mueller signed a two-year, $9.5 million deal as a free agent in the offseason, had hoped to get through a season without surgery. He wanted to make a big impression with his new team, wanted to make sure Dodgers manager Grady Little could write him into the lineup every day. ''I hate to let Grady down," Mueller said. ''I tweaked it a couple of weeks ago and I knew then, really. I didn't have to have any tests. I knew. It felt just like it did when I hurt my knee for the Red Sox in '04 when I was going for a foul pop fly in Seattle. But I wanted to see if I could play through it, and for a couple of weeks I thought I could. ''But I've been a mess. I've been making errors and haven't been hitting. I had about 50 ccs of fluid drained the other day. Had a cortisone shot, which dried up the extra fluid. I played one day on it and it swelled back up on me. I knew I had to shut it down."