Mark Dennis was a 6' 6" offensive lineman out of the University of Illinois. He was drafted in the eighth round of the 1987 NFL Draft by the Miami Dolphins with the 212th overall pick.
In Dennis' rookie season, the strike-shortened, replacement-fiasco 1987 season, he appeared in five games for Miami, starting two from the left guard position when injuries felled starter Roy Foster.
In 1988 Dennis appeared in 13 games, starting seven from the left tackle slot. He helped protect Dan Marino suffer an NFL low six sacks. He also helped pave the way for Miami's running back-by-committee approach, featuring Lorenzo Hampton, Troy Stradford, Ron Davenport and Woody Bennett. The four combined for 1137 yards and 11 touchdowns on 298 carries.
In 1989, Dennis suffered from a knee injury, restricting him to eight games and only one start.
1990 would see Dennis join the starting unit for all 16 games at right tackle. Dan Marino again led the NFL in fewest sacks, with 11, while Sammy Smith rushed for 831 yards and eight touchdowns. In 1991, he stayed in the starting lineup for 16 more games.
1992 and 1993 would see Dennis serve the Dolphins in diminishing capacities. He joined the Cincinnati Bengals for the 1994 season, and would also later play two seasons with the Carolina Panthers before retiring.
In seven seasons with the Dolphins, Dennis would start 50 of the 90 games in which he appeared.