As the
NFL did not officially maintain
sack records until 1982, he unofficially led the Dolphins in sacks in 1972 with 10; Den Herder also unofficially led the team in 1975 with a career high 11 sacks. He was named All-AFC in 1972. In October 1973, he unofficially tied
Bill Stanfill for most sacks in a single game with 5, as Stanfill had recently surpassed the previous total just two weeks earlier. Also, he unofficially led the Dolphins in sacks during the 1978 and 1979 seasons with 9. His unofficial total of 64 sacks ranks fourth on the Dolphins sack list. In addition to his five-sack game in 1973, Den Herder recorded two four-sack games (September 22, 1974, at Buffalo Bills) and (November 11, 1979, vs. Baltimore Colts). ==Retirement and post-football career==