Per Steve Bulpett of the Boston Herald, Williams and Evans are Boston's two main targets as it looks for offensive upgrades off the bench before the Feb. 8 trade deadline.
Celtics general manager Danny Ainge has remained aggressive as his team sits atop the Eastern Conference with a 38-15 record.
Bulpett did note the Memphis Grizzlies are seeking a first-round draft pick for Evans, but Ainge "seems to be again holding the line on what he believes is proper value."
Evans signed a one-year deal with the Grizzlies in the offseason. The 28-year-old is averaging 19.5 points per game and is shooting a career-high 39.2 percent from three-point range this season.
The Los Angeles Clippers appear to be in sell mode after dealing Blake Griffin to the Detroit Pistons on Monday. Williams is in the final year of his contract and is averaging a career-high 23.5 points per game off the bench this season.