'He's going to play," Warriors head coach Steve Kerr said to reporters less than two hours before tip-off.
Durant has not played since Game 5 of Golden State's second-round playoff series against the Houston Rockets because of a strained calf.
While Golden State managed to close out the Rockets in Game 6 of that series and then sweep the Portland Trail Blazers in the Western Conference Finals, they have been no match for the Raptors during the NBA Finals to this point.
After Golden State tied the series at 1-1, Toronto won in Game 3 against a Warriors team that was without both Durant and Klay Thompson. While Thompson returned for Game 4, the Raptors prevailed 105-92 on the road to secure a 3-1 series lead.
ESPN's Jalen Rose said on NBA Countdown that Durant attempted to go through a workout Thursday prior to Friday's Game 4, but noted that it "didn't go well on any level."
Although Golden State is still dangerous when Thompson, Stephen Curry and Draymond Green are in the lineup, Durant's importance cannot be understated.
Prior to getting injured, Durant led all players in playoff scoring with 34.2 points per game on 51.3 percent shooting.
He is also the reigning two-time NBA Finals MVP, and his absence has put essentially all of the scoring burden on Curry and Thompson during these Finals. Additionally, the Warriors have missed Durant's length and athleticism on defense to counter Kawhi Leonard and Pascal Siakam.
With Durant set to end his nine-game absence, the Warriors may have the mental edge entering Game 5 even though they trail 3-1 in the series.
Even if Durant isn't 100 percent, having him on the court should force the Raptors to take some of their defensive attention away from the likes of Curry and Thompson. Merely having him as a decoy who can chip in a bit on offense significantly increases Golden State's chances of winning Game 5 and sending the series back to Oakland for Game 6.