Havlat returned for Game 3 of the Western Conference Semifinals on Saturday after missing all but the first period of Game 1 of a first-round sweep. However, he lasted six shifts worth 4:52 of ice time before sustaining a lower-body injury.
McLellan said he did not know if the injury was related to the one Havlat sustained in the prior series against the Vancouver Canucks.
"If you're hurt and you can't play, you can't play," McLellan said. "We can be as frustrated as we want. It was hard because we had to juggle the lineup, but we talked about the difference between being injured and hurt. He's injured."
Forward Tim Kennedy could re-enter the lineup after playing Game 2 but being scratched from Game 3.
"Well, Clifford is out there practicing, and Jarret is not. So you have the same thing that I have," Kings coach Darryl Sutter said. "If Jarret is not practicing, [that] means he is following protocol. Cliffy is practicing, which means he has got the next step."
San Jose won Game 3 2-1 in overtime and trails the best-of-7 series 2-1 heading into Game 4 (Tuesday, 10 p.m. ET; NBCSN, RDS, TSN).