Prior to the 1989 season, Moon signed a five-year, $10-million contract extension, which made him the highest-paid player in the NFL at that time. In 1990, Moon led the league with 4,689 passing yards. He also led the league in attempts (584), completions (362), and touchdowns (33), and tied Dan Marino's record with nine 300-yard games in a season. That included throwing for 527 yards against Kansas City on December 16, 1990, the second-most passing yards ever in a single game. The following year, he again led the league in passing yards, with 4,690. At the same time, he joined Marino and Dan Fouts as the only quarterbacks to post back-to-back 4,000-yard seasons. Moon also established new NFL records that season with 655 attempts and 404 completions.