Gastineau was among the most talented and honored defensive linemen of his era. He made the Pro Bowl five straight seasons (1981–85) and finished his ten-year career with 107½ sacks, the Jets all-time record. He was a First-team All-Pro in years 1981-85 and was consensus All-AFC in each of those years. In New York, Gastineau was a key part of the famed New York Sack Exchange," the Jets defensive line that also included Joe Klecko, Marty Lyons and Abdul Salaam. The four combined for 66 sacks in 1981, including twenty by Gastineau (In 1981 sacks were unofficial, but Gastineau's 20 sacks trailed Klecko by only ½ a sack), to lead the Jets to their first playoff game since 1969. He was Second-team All-Pro in 1981 as well as being consensus All-AFC. In November 1981, he, Klecko, Lyons and Salaam were invited to ring the ceremonial opening bell at the New York Stock Exchange, which served as the inspiration for their nickname. With Klecko rupturing the patella tendon in his right knee in the second game of the strike shortened 1982 season against the New England Patriots, Gastineau became the new unofficial leader of the "Sack Exchange." Though he was often double teamed, he finished the season with six sacks, and was voted the NFL Defensive Player of the Year by NEA (and awarded the George S. Halas Trophy). The Jets made the playoffs again in 1982, losing the AFC Championship game to the Miami Dolphins. The 1983 season started with Gastineau and the Jets' first round pick of the 1983 NFL Draft, quarterback Ken O'Brien, getting arrested and charged with assault at Studio 54. Despite this off-the-field indiscretion, Gastineau totaled 19 sacks to lead the NFL for the first time. Gastineau was nationally famous for doing his signature "Sack Dance" after sacking an opposing quarterback. However, he had to stop when the NFL declared it "unsportsmanlike taunting" in March 1984 and began fining players for it. The ban on the Sack Dance stemmed from a 1983 game against the Los Angeles Rams, when Gastineau and Rams Pro Football Hall of Fame offensive tackle Jackie Slater got into a fight following a Gastineau sack of Rams quarterback Vince Ferragamo. Gastineau had his best individual season with an NFL record 22 sacks (leading the NFL for the second year in a row), 69 tackles and one fumble recovery for a touchdown in 1984. He was voted the UPI AFC Defensive Player of the Year, and was also named MVP of that season's Pro Bowl after tallying four sacks and a safety in that game. Gastineau's sack record stood for seventeen years until Michael Strahan broke it in 2001. New defensive coordinator Bud Carson installed a 3-4 defense for the 1985 season. Gastineau shifted from left defensive end to right defensive end, although he did move him around to allow for mismatches. Gastineau broke his hand early in that season but still finished second in the league with 13½ sacks and was voted All-Pro by the NEA. The Jets finished 11-5 in 1985 to earn a wildcard spot in the playoffs along with fellow AFC East rivals, the New England Patriots. Gastineau recorded a sack in the Jets' 26-14 loss to the Pats at the Meadowlands. For the start of the 1986 season, Gastineau was featured on the cover of Sports Illustrated alongside New York Giants star linebacker Lawrence Taylor. Injuries limited Gastineau to just two sacks in ten games (his lowest total since his rookie season) as he was slowed by groin and abdominal muscle ailments and then by a damaged left knee that required arthroscopic surgery and forced him to miss the last five games of the regular season. Gastineau rebounded in the postseason, recording a sack in the Jets 35-15 wildcard round victory over the Kansas City Chiefs and 2½ more in the Divisional Round Playoff game against the Cleveland Browns. However, late in the fourth quarter of that game, with the Jets leading 20-10 and the Browns facing a second down and 24 from their own 18-yard line, Gastineau was called for a questionable roughing the passer penalty. The play had originally resulted in an incomplete pass by Browns quarterback Bernie Kosar so instead of having a 3rd-and-24 situation, the 15-yard penalty on Gastineau gave the Browns a first down at their own 33. From there, the Browns drove the remaining 67 yards to a touchdown which cut the Jets' lead to 20-17. The Browns would later tie the game with 7 seconds remaining in regulation on a 22-yard field goal by Mark Moseley and win it on a 27-yard field goal by Moseley 2 minutes and 2 seconds into the second overtime period. After the game, Gastineau said that he hadn't been guilty of roughing and that he was "just following through." Teammate Marty Lyons, the Jets' other starting defensive end, defended Gastineau saying, "(Ben Dreith) is a referee who's known to take care of the quarterback." Joe Walton, the Jets' head coach would say only, "It was a very key play, Mark was just trying to do the best he could do." In 1987, Gastineau was the only New York Jet regular to immediately cross the picket line in that year's players' strike, citing his need to pay alimony. Teammate Dave Jennings said of this understandably unpopular move: "We expected it from Mark. He's always put himself in front of the team." Gastineau got into a fight with backup center Guy Bingham when he drove into the Jets complex early in the strike. Gastineau wound up having the last laugh of a sort when teammates Marty Lyons and Joe Klecko joined him later that season in breaking the players' strike."
