Durant, Westbrook, Harden Breakup Cost OKC 'At Least 2' Rings, Serge Ibaka Says

If Kevin Durant, James Harden and Russell Westbrook had stayed together in Oklahoma City, there would be a couple more championship banners hanging in the Paycom Center rafters ... at least, that's according to Serge Ibaka.

The former Thunder center -- who played alongside the trio of future Hall of Famers during their stint in OKC -- told TMZ Sports out at LAX this week he's sure they all would have some more championship bling in the jewelry cases if the team had just found a way to keep everyone together.

"Minimum two," he told us.

Harden, Durant and Westbrook first logged minutes together in Oklahoma during the 2009-10 season ... and it didn't take them long to prove they were a dominant force. They made the playoffs that year -- and then a few seasons later, they got all the way to the NBA Finals.

But in 2012, Harden was traded to the Houston Rockets ... and the Thunder never made it to another Finals until Shai Gilgeous-Alexander came to town.

While Ibaka noted it's very difficult to win a 'ship with or without a superstar-laden lineup, he said if they had just figured out how to make it work, OKC would've been rewarded.

As for the new iteration of the Thunder, Ibaka told us if that core can remain together ... he could see plenty more Larry O'Brien Trophies heading to Oklahoma City in the near future.

"On paper, they have a chance to win three," he said. "They're young. They're going to keep getting better and better."