Mariani attended Havre High School where he was awarded 10 letters: three each in football and basketball and four in tennis. He was named all-state at wide receiver. In his senior season he had 48 receptions for 1,237 yards and 16 touchdowns. He served as a team captain as a senior in football. His 2004 football team was 12–0 and the state “A” champion. He participated in Montana’s annual East-West Shrine Game.
Mariani, a walk-on at Montana in 2005 studying Business Marketing & Management, did not play football his first year. In 2006 Mariani played in all 14 games and had eight tackles on special teams. He did not have a reception as a receiver. In 2007 Mariani saw action in 11 games with three starts. His first touchdown came against Northern Colorado when he caught a 27-yard pass in the second quarter. Mariani finished the season with 15 catches for 231 yards and one touchdown. He also led the Big Sky and was 11th in the FCS in punt returns. As a junior in 2008 Mariani started all 16 games and 69 receptions for 1,308 yards with a career-best 15 touchdowns. His best game came against Southern Utah when he tied a school record with 4 touchdowns. He set a school record with 2,265 all-purpose yards, which is the fifth most in Big Sky Conference history. He led the Big Sky in punt returns, averaging 16.22 an attempt, which ranked him fourth in the nation. He was a first team All-Big Sky picks at both wide receiver and a returner. He was named second team All-American by the Sports Network. His best season came in 2009 when he caught 80 passes for 1,479 yards and 13 touchdowns. His 1,479 receiving yards set a single-season record at Montana. Mariani led the conference with seven 100-yard receiving games and in multiple touchdown games with four. He was a unanimous All-Big Sky pick at wide receiver, a second team selection as a return specialist and was named a first team All-American by the Associated Press. His best game came against South Dakota State when he gained 389 all-purpose yards, the second highest total in Big Sky single-game history; he recorded 12 receptions for 171 yards and two touchdowns, returned four kickoffs for 178 yards and 40 yards from six punt returns. Mariani finished his college career as one of the most successful receivers in school history with records in career receiving yards, receiving touchdowns and career all-purpose yards.
Professional career
Tennessee Titans
Mariani was drafted by the Tennessee Titans in the 7th round of the 2010NFL Draft and later signed a four-year deal with the team. In week 4, he returned a kickoff 98 yards for a touchdown. In week 11, he returned a punt 87 yards for a touchdown against the Washington Redskins. Mariani was selected to the 2011 Pro Bowl as a return specialist for the American Football Conference. Mariani set two Pro Bowl records in the 2011 Pro Bowl: number of returns and total return yards for a game. Mariani missed the entire 2012 season after he broke his leg on a first-quarter punt return in the third game of the preseason against the Arizona Cardinals. He was released by the Titans during final cuts on August 29, 2014.
On November 18, 2014, Mariani was signed by the Chicago Bears to a two-year contract. Mariani only played in six games during the 2014 season, returning 20 kickoffs for 510 yards. On January 3, 2016, Mariani caught a career-high six receptions for a career-high 80 yards against the Detroit Lions. Mariani ended his 2015 season with a career-high 26.1 yards per return but with a career low 16 returns. On March 12, 2016, Mariani was re-signed by the Chicago Bears to a one-year contract.
Tennessee Titans (second stint)
On September 5, 2016, Mariani was once again signed to the Tennessee Titans after being released from the Bears over the previous weekend. Mariani finished the 2016 season with 795 total returning yards and 0 touchdowns.
