[3] He also played for FC St. Gallen and Grasshopper Club Zürich in Switzerland, as well as Borussia Mönchengladbach and Werder Bremen in Germany.

He is currently the sporting director of Swiss Challenge League side FC Wil.

[6] In the summer 2011 he signed a four-year contract with Grasshopper Club Zürich, the Swiss record football champion.

After playing in three test games, Lang made his first team league debut on 19 July 2015 in the 2–0 home win against Vaduz.

[14] Following this, on 22 November, in the home game against Manchester United he scored the winning goal in the 89th minute as Basel won 1–0 to end the group in second position and advance to the next round.

[15] In the knockout phase, when playing Manchester City, Lang again scored the winning goal in the 71st minute as Basel won 2–1 and ended their opponent's 15-month unbeaten home run.

In June 2018, Lang joined Borussia Mönchengladbach for their 2018–19 season having agreed a four-year contract.

[19] On 29 August 2019, Lang joined SV Werder Bremen on a season-long loan deal for the 2019–20 Bundesliga season with an option to buy included.

[20] Initially Lang arrived as replacement for the injured Theodor Gebre Selassie and played four consecutive games for over 90 minutes from the third to the sixth matchday, but after that he was hardly used anymore.

[25] In the 2021–22 UEFA Europa Conference League they won their group, but were knocked out in the round of 16 losing twice against Marseille.

However, the season didn't start well for the team, two defeats and three draws in the first six matches and things continued in that manor.

In February Frei was replaced through Heiko Vogel, but at the end of the season Basel were in fifth position.

In the tenth minute of the added over-time in the second half of the extra time Basel conceded the decisive goal and were knocked out in the most bitter of ways.

On 25 July 2024 Basel announced that by mutual agreement Lang and the club had terminated their contract.

[30] It therefore turned out, that the last match of their 2023–24 season against Yverdon-Sport, which ended in a goalless draw on 21 May 2024, had been his last competitive game with the team.

[3] On 12 November 2024, he was announced as the new sporting director of Swiss Challenge League side FC Wil,[6] thus ending his active playing career.

The current sporting director, Jan Breitenmoser, will work with Lang to ensure a seamless transition, before finally departing in the summer of 2025.

[38] He was sent off in Switzerland's 1–0 defeat to Sweden in the round of 16 for denying an obvious goalscoring opportunity in the 90+4th minute, becoming the only player in to tournament to be sent off in the knockout stage In May 2019, he played in 2019 UEFA Nations League Finals, where his team finished 4th.