D.C. United Willis was selected by
D.C. United with the 50th pick in the third round of the
2011 MLS SuperDraft, and he signed a contract with the team on March 16, 2011. Willis served as the backup goalie with
Bill Hamid being the first choice goalie. He made his MLS debut on August 13, 2011, recording a clean sheet in a 4–0 victory over
Vancouver Whitecaps FC. Willis made only 3 appearances in his first season. after Willis had made 9 starts. With Hamid suspended, Willis started the next match. However, this time he couldn't replicate his heroics as D.C. United fell to the
Houston Dynamo 3–1. Hamid returned for the second leg, but D.C. United drew 1–1 and was eliminated. Willis remained the second choice goalie for 2013, only getting an extended run of games while Bill Hamid was with the
United States national team for the
2013 CONCACAF Gold Cup. Willis made 5 starts before Hamid retook the starting job on August 10. Willis enjoyed success in the 2013 U.S. Open Cup. On May 28 he saved 2 penalties against the
Richmond Kickers as D.C. United won on penalties. Willis helped lead D.C. United to 3 more wins, including a clean sheet in the semi-finals, a 2–0 win over the
Chicago Fire. In 2014, Willis became third choice goalkeeper after losing his spot as the number 2 to
Andrew Dykstra in preseason. Willis was sent on loan to D.C. United's
USL affiliate, the
Richmond Kickers. His first appearance of the season with D.C. United came in a
CONCACAF Champions League match against
Waterhouse on August 20, a 1–0 win for D.C. United. Willis made 2 more appearances in the Champions League, both of them clean sheets against
Tauro FC.
Houston Dynamo On December 8, 2014, Willis was traded to the
Houston Dynamo along with
Samuel Inkoom, in exchange for the rights for
Andrew Driver (who moved to Europe and didn't play for D.C.) and a fourth-round pick in the
2016 MLS SuperDraft. On December 19, 2014, he signed a contract with the Dynamo. Willis served as the backup to Tyler Deric for 2015 and appeared in only six games in his first year with Houston. Willis got a chance to play early in 2016 with Deric missing time for an abdominal injury. Deric returned in week 6, but he picked up a red card, with Willis coming in as a sub and starting the next game as Deric served his suspension. Willis came in for Deric again on May 15 as Deric served a suspension for another red card. Willis picked up his first career assist in the game when he hit a long goal kick that
Giles Barnes ran onto and converted to score the game winning goal over
Real Salt Lake. Willis would fill in for Deric as he missed time with another abdominal injury and an elbow injury. He also made the MLS Team of the Week for that game. He ended the season with 5 clean sheets from 26 MLS appearances. Willis's strong performances saw him named the Dynamo defensive player of the year. Despite his good play, the Dynamo missed the playoffs again. Willis missed the start of the 2017 season due to a knee injury. Willis became the number 1 goalie during the playoffs after Deric was arrested and subsequently suspended by the MLS. He would help the Dynamo defeat the
Portland Timbers 2–1 on aggregate and reach the Western Conference finals, where the Dynamo fell to
Seattle Sounders FC. Ahead of the 2018 season, Willis re-signed with the Dynamo. Off-season addition
Chris Seitz started the year as first choice keeper. Willis would retake the starting job on April 21 and keep it for the rest of the season. He enjoyed a strong performance on July 21, saving a penalty kick and being named to the MLS Team of the Week after helping the Dynamo get a 1–1 draw against rival
FC Dallas. The Dynamo would miss out on the playoffs in 2018, but they enjoyed success in the
US Open Cup. Willis started the Open Cup semifinal match up with
LAFC on August 8 as the Dynamo won on penalties. Willis kept a clean sheet in the final to help Houston defeat the
Philadelphia Union 3–0 as the Dynamo won their first Open Cup in club history. Willis began 2019 as the club's first choice keeper. He played in every game of the
CONCACAF Champions League as the Dynamo reached the quarterfinals. Willis returned on August 11, a 2–1 loss to the Union. He started the next 8 matches before sitting the final 2 of the season in favor of Deric. It was another disappointing league campaign for Houston, failing to qualify for the playoffs for the second straight season.
Nashville SC On November 19, 2019, Willis was traded to
Major League Soccer expansion side
Nashville SC in exchange for
Zarek Valentin. He made his debut for Nashville on February 29 in Nashville's first ever MLS game, a 2–1 loss to
Atlanta United FC. In a shortened season due to the
COVID-19 pandemic, Willis made 23 appearances, out of a possible 23, and kept a league best 9 clean sheets. He also was named to the MLS Team of the Week twice during the season. Willis led a Nashville defense that conceded the 3rd fewest goals in MLS, leading the team to a 7th place finish in the Eastern Conference and qualifying for the playoffs. In Nashville's first ever playoff game, Willis kept a clean sheet to help defeat
Inter Miami CF 3–0. He kept another clean sheet in their next match as they defeated
Toronto FC 1–0 in extra time. In the conference semifinals, Nashville and Willis lost to the
Columbus Crew 2–0 in extra time. == Career statistics ==