He was a four-year starting offensive tackle for Southeast Missouri State, and was in All-Conference teams for four consecutive seasons, and finished his collegiate career with 46 consecutive starts.
Connolly was signed by the Jacksonville Jaguars as an undrafted free agent on April 24, 2005. He made the team's 53-man roster and spent the rest of the season on it. He was placed on injured reserve by the Jaguars on September 2, 2006. Connolly was waived by the Jaguars on September 1, 2007.
Connolly was signed to the New England Patriots' practice squad on September 13, 2007, where he spent the remainder of the season before being re-signed to a future contract on February 5, 2008. He was then waived by the Patriots on October 20, 2008. He was re-signed to the team's practice squad on October 22. He was promoted to the active roster on December 13, 2008. Connolly made the 53-man roster in 2009 and started four games at right guard in place of an injured Stephen Neal. During the season, he received a contract extension through the 2011 season. With veteran starter Logan Mankins missing from the first seven games of the 2010 season due to a contract situation, Connolly started all of those games in his place at left guard. He was a reserve for the team's Week 9 game, but returned to the starting lineup at right guard following a season-ending injury to Neal. In a December 19, 2010 game against the Green Bay Packers, Connolly set the record for the longest kickoff return by an offensive lineman in NFL history, returning a squib kick 71 yards to set up a Patriots touchdown. Connolly was named AFC Special TeamsPlayer of the Week for the feat. Connolly suffered a concussion in the game and missed the final two games of the regular season. He finished the 2010 season with 13 starts in 14 games played. At the end of the 2011 season, Connolly and the Patriots appeared in Super Bowl XLVI. He started in the game, but the Patriots lost to the New York Giants by a score of 21–17. On September 3, 2014, Connolly was named one of the Patriots' six team captains. On February 1, 2015, he was part of the Patriots team that won Super Bowl XLIX over the Seattle Seahawks, 28–24.
Retirement
A free agent after the 2014 season, Connolly fielded interest from multiple NFL teams. However, on July 16, 2015, Connolly retired, citing family stability, concussion injuries and winning the Super Bowl as contributing factors.
Personal life
Dan is married to Lori, and they have four daughters.