League sources told ESPN's Adrian Wojnarowski that there continues to be no structural damage in Irving's knee, and that there is still a strong belief that rest will be the best remedy to facilitate his eventual return to the lineup.

Irving missed his fourth straight game Tuesday night while waiting for soreness to dissipate in the knee. Stevens suggested he's unlikely to join the team for the start of its upcoming four-game road trip out west.

"Still the same thing that we've been talking about. That knee has been sore," Stevens said before the team's 100-99 win against the Thunder. "But he worked really hard to manage it throughout the entire season, and I think he's had some pretty good days recently, so I'm encouraged by it in the big picture."

Irving first acknowledged soreness in his knee, the same one he had surgery on during the 2015 Finals while with the Cavaliers, after a loss in Houston earlier this month. Irving has not played since missing the second half of a loss to the Indiana Pacers on March 11.

"He's out because of knee soreness, not because we're choosing to rest him," Stevens said. "That's the bottom line. ... We've talked about it, we want him to feel 110 percent. He wants to feel 110 percent."

The Celtics seem firmly entrenched in the No. 2 seed in the Eastern Conference, and that's been key as the team deals with a rash of injuries. Last week, rookie big man Daniel Theis and veteran guard Marcus Smart underwent surgery. Theis is out for the season after tearing his meniscus; Smart hopes to return in the playoffs after tearing a ligament in his thumb.

Boston also is playing without Jaylen Brown (concussion protocol) and Gordon Hayward (ankle rehab).

"Obviously, we're fortunate in that we created cushion early on in the year as far as playoffs and everything else, but this is not one of those situations where we're choosing to rest somebody," Stevens said. "He's out because he's got a sore knee."

Stevens stressed that the soreness is not a new pain but just lingering.

"Just continued soreness is what's made the decision not to play tonight, and made the decision to not go on the trip, and seek outside counsel," he said. "It's not new pain by any means, nothing new. Continued soreness."

During a radio appearance last week, Celtics general manager Danny Ainge said Irving might eventually need offseason surgery to remedy the lingering soreness.

"He has a surgery that may need to happen," Ainge told the 98.5 The Sports Hub. "But maybe not this summer, maybe the following summer or maybe the summer after that. I think that he could probably do it any time he wanted but I'm not sure that it's needed at this moment."

Irving has said he hopes he doesn't require any offseason procedure but noted after the Pacers game that he wanted to take an extended rest in hopes of combating the soreness that has plagued him this month.