Kemba Walker has historically been among the most durable players in all of basketball. He didn't miss a single game until his third season in the league and had missed only six in total over the past four seasons. When the Boston Celtics signed him to a four-year max contract this offseason, they did so with relative confidence that he would be on the court for most of that time. 

But accidents happen, and that looks to be the case right now, as Walker suffered a scary injury against the Denver Nuggets on Friday. While trying to control a pass that he deflected, Walker ran headfirst into the chest of teammate Semi Ojeleye. He was immediately taken off the court on a stretcher. 

The team announced that Walker is suffering from "concussion-like symptoms," and that he was being taken to a hospital for further evaluation. According to Adrian Wojnarowski of ESPN, the early indications point to Walker not having suffered a serious injury in the play, which would be a major relief for Boston. Coach Brad Stevens announced after the game that all of the tests and scans on Walker that came after the game had positive results. 

Head and neck injuries are fairly uncommon in basketball. This play was just a freak accident. Nothing could have prevented it, and now the Celtics, and anyone watching, can only hope that it is not as serious as it appears. 

If it is, the injury threatens to derail what has been an incredible start to the season for the Celtics. At 11-3, they are currently in second place in the Eastern Conference despite already losing Gordon Hayward to an injury earlier in the season. With Hayward slated to return eventually and plenty of trade assets to work with, a healthy Celtics team would have been among the favorites to reach the NBA Finals and potentially win it. 

Walker had been at the center of that. He is Boston's leading scorer at 22.6 points per game, and has made over 39 percent of his 3-point attempts. Further, his decision to sign with the Celtics helped the team get over the free-agent losses of Kyrie Irving and Al Horford. His presence has seemingly led to improved team chemistry, and young players like Jayson Tatum and Jaylen Brown have taken major steps forward by his side. 

But if this injury does indeed keep Walker out for an extended period, it would not be the first time Boston has suffered this sort of calamity with a star free-agent addition. Hayward infamously suffered a severe foot injury in his very first game with the Celtics. He struggled in his return to the court last season, and now that Boston has spent most of their draft capital and financial flexibility, weathering another long-term storm in terms of injuries could derail Boston's entire plan for contention over the next few years.