Head athletic trainer Stan Conte said Wednesday that Benitez has flown to Miami to begin rehab with physical therapist Lisa Kearns, who has expertise working with baseball players.
"He won't be back this year," said Conte. "We're optimistic he'll regain his strength and his knees will calm down the way it was before. He should be able to go to Spring Training without any problems."
If rehab doesn't work, other options will be explored, including arthroscopic surgery. Conte explained it will take about six weeks to determine how the knees will fare.
When Giants general manager Brian Sabean was asked if Benitez, who earned $4 million plus $2.6 million of a $7.4 million signing bonus this season, would be back in 2007, his reply was, "He'll still be under contract."
Sadler pitched seven games for Fresno, compiling a 2-0 mark and 1.80 ERA with 12 strikeouts. At Double-A Connecticut, the 24-year-old was 4-3 with a 2.56 ERA and 20 saves over 44 games, striking out 67 in 45 2/3 innings.
Sadler is expected to join the team Thursday.
"He has a good arm," said Alou of the reliever. "He throws hard and he has a good breaking ball plus a curve and slider."
This year, Benitez had a testy relationship with San Francisco fans, who booed him on multiple occasions, even when he saved games. Last season, the closer tore his hamstrings and missed 3 1/2 months following surgery yet managed to save 15 games in 17 chances.
Ths year didn't start much better, with Benitez on the disabled list with left knee bursitis.
Veteran Mike Stanton, acquired from Washington on July 28, replaced Benitez, going 1-0 with five saves over nine scoreless outings.