Jens Martin Gammelby

During the 2019–20 season under new head coach Niels Frederiksen, Gammelby continued to struggle to make the starting lineup, with Frederiksen preferring Mensah and Larsson at his position. As Brøndby transitioned into a 3–5–2 formation during the fall, and left back Anthony Jung began playing in central defense with Mensah transitioning to the left back position as well as Larsson's contract expiring, Gammelby was expected to play more regularly during the latter half of the season.

In May 2018, it was reported that Gammelby would leave Silkeborg IF to join Brøndby IF in summer 2018, having agreed to a five-year contract after a breakout season for Silkeborg. He was handed shirt number 2. On 29 July 2018, Gammelby made his debut as a substitute against Hobro IK, which ended in 2–1 win. During his first season in Brøndby, he struggled to make the starting lineup with head coach Alexander Zorniger preferring first Johan Larsson and since Kevin Mensah at the right back position. Gammelby made 17 appearances and scored one goal during his first season at the club.

Gammelby made his Danish Superliga debut on 27 March 2014 in a 1–0 win over Hobro IK, where he was in the starting line-up.

In April 2014, Gammelby signed a contract extension, keeping him in Silkeborg until 2017. Gammelby was playing on fulltime in Silkeborg IF from the summer 2015.

Jens Martin Gammelby (Danish pronunciation: [ˈjens ˈmɑːtsʰin ˈkɑml̩ˌpyˀ] ; born 5 February 1995) is a Danish footballer who plays as a right back for Danish Superliga club Brøndby IF.