Before the 1988 San Diego Chargers season began, Dan Fouts chose to retire from the game after 15 seasons, leaving Vlasic as the main backup to starter Mark Herrmann, and as a result the Chargers began trying to trade for an experienced quarterback. The Chargers also signed Mark Malone and Babe Laufenberg to compete for the starting job, and traded Herrmann to the Indianapolis Colts. After months of training and the 1988 preseason, Vlasic began the season as the third-string quarterback behind Malone and Laufenberg, who won the starting job. In November, after Laufenberg was injured, the Chargers decided to make Vlasic the starter instead of Malone due to the latter's ineffectiveness, as well as a six-game losing streak. He made his season debut against the Atlanta Falcons on November 13, and threw for 190 yards in a 10–7 victory. As a result of his performance, coach Al Saunders said that Vlasic would have the starting job for the rest of the season. Vlasic's second start came against the Los Angeles Rams where he threw for 80 yards and a touchdown. However, he suffered torn ligaments in his left knee late in the third quarter, and was lost for the season. He finished the season with 25 of 52 passes completed and a passer rating of 54.2.