DeBerg posted a career-high 395 yards passing against Denver on September 17, 1990. He seriously injured his non-throwing hand in a loss to the Houston Oilers on December 16, which required the insertion of a pin into his broken finger to keep it straight. For their last two games and the playoffs, the Chiefs ran their offense out of the shotgun formation to protect DeBerg from having the football jammed in his injured hand during the center-to-quarterback exchange. Kansas City won those games to clinch their second playoff appearance in over a decade, with DeBerg completing 44 of 59 passes for 527 yards with two touchdowns and no interceptions. In a 17–16 loss to the Miami Dolphins in the 1990 AFC wild-card game, he completed 17 of 30 pass attempts for 269 yards with one touchdown and one interception.