Cavaliers activate center-forward Williams
In addition, first-round draft pick Luke Jackson remained on the team's injured list with back spasms that could sideline him for the season.
"I don't know exactly what the situation is with Luke," coach Paul Silas said. "We're still waiting for complete word from the doctors. They said it is a condition that would probably only allow Luke to play at 70 percent this season."
Jackson, selected 10th overall in 2004, declined comment in the locker room before Cleveland played the New York Knicks.
Williams, 36, missed five games with left knee tendinitis. In 17 games this season, he is averaging 1.9 points and 1.6 rebounds.
Diop, 22, has played only 166 minutes in 15 games, averaging 0.9 points and 2.7 rebounds.
The procedure was performed by Dr. John Belzer at the Health South Surgery Center in San Francisco.
Placed on the injured list Monday with soreness in the knee, Najera is expected to be sidelined for two to three weeks.
Known for his tough defense, Najera is averaging 4.1 points and 2.4 rebounds in 27 games this season.
Kittles, who has played in just five games this season, was activated from the injured list on Saturday after being sidelined with a bulging disk in his lower back. He had been placed on the injured list for the second time this season on December 21.
Kittles had arthroscopic surgery on the knee before the Clippers acquired him from the New Jersey Nets this summer for a second-round pick and cash considerations.
Penciled in as the team's starting shooting guard, the 6-5 Kittles is entering the final year of a five-year, $52 million contract. He averaged 13.1 points while playing all 82 games last season and has career averages of 14.3 points and 3.9 rebounds in 496 games.
This season, Kittles is averaging 5.8 points, 1.8 rebounds and 2.4 assists.
In a corresponding move, the Clippers placed guard Marko Jaric on the injured list with a stress fracture in his right foot. Jaric, who has missed the last eight games and is expected to be sidelined for three more weeks, has averaged 11.0 points and 6.4 assists in 23 contests this season.
Information from The Associated Press was used in this report.