Midfielder Cleber Santana, 35, played alongside De Gea at Atletico Madrid and was one of 71 people to be killed when their plane plunged into a mountainside in Medellin, Colombia on Monday night.
Only three members of the squad survived, while manager Caio Junior, the coaching staff, members of the crew on board and 21 journalists lost their lives.
Like many figures within the football world, De Gea took to social media to express his sorrow at the tragedy.
The Spaniard tweeted: "Deeply affected by Medellin's plane crash. I shared locker with Cleber Santana and it's difficult to reveal how I feel. A huge hug."
The team were on their way to compete in the final of the Copa Sudamericana for the first time in the club's history.