Okung, entering his 10th season in the NFL, announced Thursday on Twitter that he went to urgent care on June 1 after experiencing "unusual chest pain" at practice.
The doctor told Okung that his decision, which he viewed as precautionary, likely saved his life.
The two-time Pro Bowl selection suffered a pulmonary embolism from blood clots in his lungs.
Melvin Gordon is in the final year of his rookie contract and holding out in hopes of a new contract.
Entering his 5th season in the NFL, Gordon has had only one 1,000-yard season, but has been a touchdown machine, finding the end zone 38 times in 55 games.
Gordon rushed for 885 yards and 10 touchdowns last season and had 490 receiving yards with another four receiving touchdowns.