Sullivan entered the league when the Minnesota Vikings used a sixth-round pick on him in 2008. The Notre Dame product established himself as a starter in 2009 and became a reliable cog in Minnesota's offensive front.
He started 93 of 96 games from 2009 through 2014, although he missed the 2015 campaign because of back surgeries.
While he started just one contest as a backup with Washington in 2016, Rams head coach Sean McVay was the offensive coordinator and saw enough to bring him to Los Angeles in 2017. Sullivan proceeded to start 15 contests and anchor the offensive line as the Rams won the NFC West.
"He's been just as important as anybody on this team and everything's he's brought to the table offensively," quarterback Jared Goff said during the year, per Lindsey Thiry and Gary Klein of the Los Angeles Times. "His ability to handle so much up front, take so much off my plate and so much off a lot of guys' plates up front."
Sullivan's offensive line finished the season as the third-best run-blocking unit in the league and the ninth-best group in pass protection, per Football Outsiders.
Goff made significant strides after he threw five touchdowns and seven interceptions in seven games in 2016 and finished with 3,804 passing yards, 28 touchdown throws and seven picks in 15 games in 2017. Running back Todd Gurley was an MVP candidate with career highs nearly across the board of 1,305 rushing yards, 788 receiving yards and 19 total touchdowns.
While Sullivan will be 33 years old during the 2018 campaign, he proved he still had plenty left in the tank while helping lead the Rams to the playoffs for the first time since the 2004 season.
Los Angeles hopes he can replicate that impact as its attempts to take the next step as a potential Super Bowl contender.