He came from AGF's 1988-born Danish Youth Championship-winning team, a side that included Morten Beck Andersen, Frederik Krabbe, Michael Vester, Niels Kristensen, Jesper Blicher and Anders Syberg.

Lumb was named the young gun "Shooting Star" of the autumn season 2007–08 by the Danish newspaper Ekstra Bladet.

[3] In Zenit, Lumb faced a tough competition for a left back position with likes of Slovak international Tomáš Hubočan, and as a result did not play much.

Lumb was initially loaned out to Dutch side Feyenoord, but the move proved unsuccessful, as he was of cause relegated to the bench and then in the stands.

[11] Upon signing, manager Ove Pedersen called Lumb "mentally very strong" and stated that he needed to work on "getting his career back on track".

[12] A few days later, OB director of sports Jesper Hansen revealed, that he had negotiated a contract with Lumb, but that the latter had eventually decided to sign with Vestsjælland.

[15] He finished the 2013–14 season with 30 total appearances,[8] as FCV ended in ninth place in the league table, six points clear of relegation.

[8] Vestsjælland suffered relegation from the Superliga at the end of the season and Lumb's contract expired, making him a free agent.

[29] After signing, Lumb said that he could still develop as a player and praised manager Bo Henriksen's style of play which involved attacking full-backs.

[30] He made his debut on 16 September in a 3–2 league win over his former club AGF, coming on as a substitute in the 83rd minute for Hallur Hansson.

In the 43rd minute, he fired a long-range shot at AGF-goalkeeper Kasper Kristensen, who failed to save the ball, which bounced off his gloves and into the net.

[39][40] On 4 January 2021, it was announced that Lumb had signed a one-year contract with Brøndby, replacing regular left-back Blas Riveros who had suffered a season-ending injury.

[41][42] He made his official debut for the club on 4 March as a starter at left wing-back in manager Niels Frederiksen's 3–5–2 formation.

[48] His first goal for the club came on 13 May, slotting home a low cross from a corner kick to deliver the 1–0 winner against HB Køge.