[3] Gjesing made his official debut as an 18-year-old only a month after signing the contract, coming on as an 88th-minute substitute in a 4–0 away defeat in the Danish Superliga to future champions Brøndby IF on 21 November.
[6] In May 2006, towards the end of the 2005–06 season, he signed three-year contract extension which AGF sporting director Brian Steen Nielsen called "justified [...], he has a good potential and, not least, a tremendous will which can bring him far.
[6] Gjesing's inconsistent performances for the first team caused some speculation as to whether AGF would offer a contract extension, as players such as Kasper Povlsen, Niels Kristensen and Martin Mikkelsen had surpassed him at his position.
[21][6] Gjesing had a frustrating start to the 2009–10 season, scoring own goals in consecutive matches against FC Midtjylland and HB Køge in the fall which ended up costing AGF four points.
[22] His disappointing season continued after the winter break, receiving back-to-back red cards in pre-season friendlies and missing a decisive penalty kick against OB on 21 March 2010.
Hobro sporting director, Jens Hammer Sørensen, called the deal a "scoop" and attributed the strong ending to the first half of the 2011–12 season, where the team conceded no goals in the last three games, to Gjesing's performances in defense.
[34][35] Gjesing returned to play for Jutland Series (fifth highest division in Denmark) club Fuglebakken KFUM Århus in November 2015, more than three years after retiring from professional football.
[37] Gjesing would go on to make 12 total appearances for the Danish under-21 team, including two legs in the 2009 UEFA European Under-21 Championship qualification play-offs against Serbia U21, which were lost 0–2 on aggregate.
[41][42][43] On 19 November 2018, Gjesing was appointed as the head coach of VSK Aarhus, a merger team in which his first youth club, Vejlby IK, formed one half.
[48] After retiring from professional football, Gjesing took a Bachelor's degree in Marketing management at Business Academy Aarhus in Viby J while attending courses for coaching licenses.