At the end of the 2013–14 season, Sommer won the league championship with Basel. They also reached the final of the 2013–14 Swiss Cup, but were beaten 2–0 by Zürich after extra time.
At the conclusion of the 2013–14 season, Sommer's leadership paid off as Basel secured the league championship. Although they had a strong run in the Swiss Cup, ultimately falling short against Zürich in the final.