The team said Durant has a "Jones fracture," a broken bone at the base of the small toe.
Thunder general manager Sam Presti said no specific incident caused the injury; it happened over time. Durant has not been given an official timetable, but will likely miss six to eight weeks, based on the typical recovery time for an injury of this nature.
"From what I've been told, a Jones fracture is the most common surgical procedure performed on NBA players as of late," Presti said. "It has happened enough so that there is enough of a body of work to look at an average recovery time."
Durant will undergo further evaluation and consultation over the next few days and determine if surgery is necessary. It appears likely.
"We're heading in that direction," Presti said.
Following practice Saturday, Durant informed the Thunder medical staff he was experiencing an "aching" in his right foot. Durant had participated in both the Thunder's preseason games thus far and played a total of 30 minutes.
"We're really fortunate that we're catching it when we're catching it," Presti said. "We are very fortunate that Kevin notified us yesterday and that we're kind of catching it on the front end, before this became more of an acute issue."
Most recently, Durant played 18 minutes Friday against the Mavericks, but Presti said there's no specific play to point to for when the injury occurred.
"Because it's a stress injury, it happened over time," Presti said. "The fact that Kevin mentioned it when he did is a real fortunate piece of this because if he had continued to play on it, it would continue to get worse. So, that it was identified when it was identified and that the pain or achiness was enough to mention it is a positive."
Durant, the reigning league MVP who averaged 32 points, 7.4 rebounds and 5.5 assists in 81 games the past season, has played the most minutes in the league since 2007 (20,717). Because of the wear and tear, Durant withdrew his name from USA Basketball this summer for the World Cup in Spain, citing need for rest both physically and mentally.
Kobe Bryant was limited to six games last season after injuries to his Achilles tendon and knee. He said Durant could return from the injury a better player.
"It's tough," Bryant said. "He's just got to be patient and do what he can in the interim. Study the game and try to improve the mental aspect, which is always what I tried to do when I was out."
Durant, entering his eighth season, has only missed a total of 16 games.
"Coming in to this season having not played USA Basketball, reflecting on that decision now, I think clearly, probably helped him a great deal, just the amount of stress he was able to avoid at that point in time," Presti said. "I think that brought him back in to camp in a good spot."
Presti said there were already discussions internally that the Thunder would try to reduce some of Durant's minutes load this season. Although he just turned 26, Durant routinely plays close to 40 minutes a night.
"I think that's certainly something that's been talked about internally," Presti said. "Hard to say exactly if that will change, but we were already accounting for that, regardless. Whether or not there will be a significant change in that, that will be up to the medical department in terms of how we get him back on the floor and when and at what loads."
The injury is one that could conceivably be played on, though that would only risk more severe, long-term damage, and the fact it's October helps ease any thought of Durant doing that.
"He could be playing on it today, but he'd be doing further damage to it, and eventually, we'd have more of an issue," Presti said. "So we need to be in position where we're thinking long-term, and the long-term includes the short-term. I think that's important to recognize."
Get well KD! Speedy recovery 🙏— Paul George (@Yg_Trece) October 12, 2014
Durant was forced to carry a heavy burden for the Thunder the past season, as teammate Russell Westbrook missed 36 games because of a knee injury. During that time, Durant erupted and scored at least 25 points in a stretch of 41 straight games, en route to his first MVP trophy. During Westbrook's absence from late December through the All-Star break, Durant averaged 35 points and 6.3 assists as the Thunder went 20-7.
Westbrook, however, has only played five games without Durant over the past five seasons. One was a season finale in which Durant sat for rest and Westbrook played just seven minutes to keep a consecutive-games-played streak intact. In the other four, during the 2010-11 season, the Thunder went 3-1 as Westbrook averaged 26.7 points and 7.0 assists and attempted 22.5 shots per game.
The past season, Westbrook only played 41 of his 1,411 minutes without Durant alongside him on the floor. In that time, he attempted 35 shots and scored 46 points. Presti said the Thunder will attempt to compensate for the loss of Durant collectively, though the bulk of burden will assuredly fall to Westbrook.
"In regard to replacing a player like Kevin Durant, you don't replace Kevin Durant. It's not going to be one person. It's going to be a collective mindset," Presti said. "We know we're a better basketball team with Kevin Durant on the floor. But we can have some influence on how good we are in the meantime. We're certainly not going to be looking at the calendar, waiting for him to get back. I don't think he'd want us to do that."
The Thunder have unfortunately been bitten often by the injury bug, with both their 2013 and 2014 playoff campaigns derailed by significant injuries. Westbrook suffered a torn meniscus in Game 2 of the Thunder's opening-round series against the Rockets and missed the remainder of the postseason, while Serge Ibaka missed the first two games of the Western Conference finals with a severe calf strain.
"You have to be able to deal with uncertainty and ambiguity," Presti said. "If [you] can only operate [when] the wind is blowing out for you, I don't think that's the mark of an elite team or an elite organization. And I think Kevin is at his best when he has to experience something different. I think he'll find something good from this."
Information from ESPNLosAngeles.com's Arash Markazi was used in this report.