Boston Celtics point guard Kyrie Irving, not pleased with the lack of progress on his sore left knee, is expected to seek a second opinion, according to multiple reports. The news was first reported by Shams Charania of Yahoo! Sports.

With lack of progress on his ailing left knee, Celtics All-Star Kyrie Irving plans to travel for a second opinion later this week, league sources tell Yahoo.

— Shams Charania (@ShamsCharania) March 20, 2018

Later, Celtics coach Brad Stevens confirmed Irving getting another opinion on his knee, writes Chris Forsberg of ESPN.com. He has missed four straight games since first injuring the knee in a March 11 loss to the Indiana Pacers. He sat out last night’s 100-99 comeback win against the Oklahoma City Thunder and first acknowledge soreness in the knee after a loss to the Houston Rockets earlier this month.

Here’s more from Forsberg on what looms ahead for Irving:

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.

…

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.”

…

“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.”

…

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.”

Irving is averaging 24.7 points, 5.2 assists and 3.8 rebounds per contest while shooting 49.1 percent from the field and 40.8 percent on 3-pointers.