Kyrie Irving is still out for the Boston Celtics after missing a fourth consecutive game due to a sore knee as he will now seek outside counsel.

Irving was first unavailable after experiencing knee soreness during the Celtics’ 99-97 loss to the Indiana Pacers on March 11 as he failed to return to the court after half-time.

Celtics coach Brad Stevens recently revealed that the former Cavaliers star was feeling "better and better" and that there was a chance of him featuring in Sunday's 108-39 loss against the New Orleans Pelicans, only to pull out in the last second.

But after now missing the Boston side's 100-99 win over the Oklahoma City Thunder on Tuesday night, Stevens revealed that Irving will not travel with the side for their upcoming four-game trip on the road and will instead seek another opinion on his knee.

"Still the same thing that we've talking about. That knee has been sore," Stevens said, according to ESPN. "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. That's the bottom line. ... We've talked about it, we want him to feel 110 percent. He wants to feel 110 percent. 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. It's not new pain by any means, nothing new. Continued soreness," he said.

The Celtics have already confirmed their place in the NBA playoffs but have seen Irving's absence coincide with a run resulting in three losses in their last five games, including the loss in Indiana where the 25-year-old last featured.

With other absentees in the likes of Jaylen Brown, Gordon Hayward, Daniel Theis and Marcus Smart, Stevens admitted the Celtics were fortunate with their early regular season form that has seen them hold a firm grip on second place in the Eastern Conference, behind the Toronto Raptors. However, he remained insistent that Irving is not being rested just because the playoffs are approaching.

"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 added. "He's out because he's got a sore knee."

Meanwhile, Celtics general manager Danny Ainge revealed last week that Irving could use the offseason to undergo surgery to fix the soreness in his knee. Irving notably had surgery on the same knee during the 2015 NBA Finals and first complained about the soreness in the 123-120 loss to the Houston Rockets on March 4 earlier this month.

"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."