He established himself as the starting goalkeeper, spending two seasons with the Terrapins before joining German club SC Freiburg, being assigned to play with the reserves.

In April 2021, Steffen won his first career trophy, starting in the final of the EFL Cup; he kept a clean sheet as Manchester City beat Tottenham Hotspur 1–0.

In January 2024, Steffen agreed to leave Manchester City and returned to Major League Soccer for the first time since 2018, signing with the Colorado Rapids.

[3] Born in Coatesville, Pennsylvania, Steffen began playing soccer at the age of five with local rec league West Bradford Youth Athletics (WBYA).

[9] He was part of the team that won the 2012 Generation Adidas Cup, defeating the Toronto FC Academy in a penalty shootout; the squad also included future pros Connor Maloney, Zach Pfeffer, Drew Skundrich, Brian White, and Zach Zandi, as well as future Penn State kicker Joey Julius, and was coached by Jim Curtin.

[14] He brought his hot form into the postseason, making five saves to help Maryland win the 2013 ACC Men's Soccer Tournament[15] and earning himself an All-Atlantic Coast Conference Freshman Team selection.

[16] In the 2013 NCAA Division I Men's Soccer Tournament, Steffen made 18 saves in the Terrapins' five matches, helping Maryland make a run to the national championship game; they fell there to Notre Dame by a 2–1 scoreline.

[31] Steffen joined the Crew after third-string goalie Matt Pacifici had his season ended by concussions,[32] but was still behind Steve Clark and Brad Stuver on the depth chart.

[37] He wouldn't relinquish the job, starting all 34 regular season games for the Crew and leading the club to an MLS Cup Playoffs berth after missing out in 2016.

[25] Steffen missed time during the 2018 season due to international commitments, as well as a mid-season knee injury,[42] but still went on to make 32 total appearances on the year.

[25] In one nine-match stretch, ranging from a victory over San Jose Earthquakes on April 28 to a defeat against Atlanta on June 13, Steffen recorded a 525-minute shutout streak, the longest in Crew history.

[44] Steffen replaced starting goalie Brad Guzan at halftime and made two saves, but failed to make a stop in the penalty shoot-out as Juventus scored on all five kicks.

[45] In the 2018 MLS Cup Playoffs, Steffen repeated his heroics from the previous year: against D.C. United in the knockout round, he saved two kicks in the penalty shoot-out as the Crew advanced.

"[49] Following the season, however, a bid starting at £7 million arrived from fellow English club and defending Premier League champions Manchester City and was accepted by the Crew.

[54] Düsseldorf sporting director, Lutz Pfannenstiel, noted that Steffen was the "perfect example of a modern goalkeeper" while discussing that he had been scouting the player since he worked at TSG 1899 Hoffenheim.

[56] Steffen started the club's first 17 matches, but suffered an injury to his patellar tendon that kept him out of action throughout the Bundesliga winter break and the COVID-19 pandemic stoppage.

[60] Steffen was included in the City squad for the first time in the opening game of the season against Wolves[61] and made his debut only three days later, starting against Bournemouth in the League Cup third round, winning 2–1 at the Etihad Stadium.

[62][63] Steffen made his UEFA Champions League debut on December 9, 2020, against Olympique de Marseille in the last game of the group stage, keeping a clean sheet in a 3–0 win.

[69] On December 7, he made his second appearance in the Champions League during his career when City lost 2–1 to RB Leipzig at Red Bull Arena.

[73] On January 4, 2024, Steffen returned to the United States, joining MLS side Colorado Rapids on a three-year contract with an option for a further year.

He made his second appearance in a friendly against Paraguay, recording his first clean sheet in a 1–0 victory, on March 27, 2018, at WakeMed Soccer Park in Cary, North Carolina.

[citation needed] Steffen is a co-founder of VOYCENOW Foundation, a non-profit organization that brings athletes and fans together to help Black communities in America and fight for equality.