The towering 6ft 6ins centre-back grew up in Denmark, where he spent time at several clubs as a youngster including Brøndby, not long after the club had enjoyed a trophy-laden spell of 10 league titles in the space of just two decades.
After laying the foundations in his home nation, it was over in Germany where Vestergaard’s footballing success for both club and country truly took off. While at Hoffenheim, he represented the German side’s youth team during the 2010/11 season, and also played for Denmark at Under-18s and Under-19s level.
Such were his impressive performances, he was selected by Marco Pezzaiuoli to make his first team debut as a late substitute in Hoffenheim’s Bundesliga win over Eintracht Frankfurt on 16 April, 2011.
Then came a breakthrough a brace of breakthrough seasons for 1899, as the imposing defender made a combined 41 appearances across 2011/12 and 2012/13, all while furthering his international profile at Under-20s and Under-21s level.
The latter campaign, meanwhile, included a maiden senior goal against Kaiserslautern, and he developed a knack for netting late on in the season after scoring against Augsburg towards the tail end of 2013/14, which also saw him make 25 senior appearances.
Recognised as one of Denmark’s best young talents, it was during that campaign that he made his maiden senior international appearance against Poland, and there was more to come in 2014.
A dramatic late leveller against Freiburg proved to be one of three goals in 26 games for club and country, with another coming at the 2015 U21 European Championships against Czech Republic in Prague.
It was in the summer of 2015 that Vestergaard’s Hoffenheim career came to an end, as he switched one Bundesliga side for another by moving to Werder Bremen.
Further club and international experience followed, with his four goals in 39 appearances across all formats including a late EURO knockout strike against Sweden, with City stopper Kasper Schmeichel also on the pitch.
However, his stay at Bremen came to an end the following summer, when a move to Borussia Mönchengladbach saw him play in European competition for the first time. With Mönchengladbach in the UEFA Champions League, the Dane featured in four of his side’s group matches, facing Barcelona, Manchester City and Celtic, before finishing third in their pool and later reaching the UEFA Europa League’s Round of 16.
By the end of the 2016/17 season, he had made a hefty 49 appearances for Mönchengladbach and Denmark – a sign of not only his ability, but also his consistency at the heart of defence.
His final season in Germany, where he had spent eight years at three separate teams, saw him score on three occasions in 34 matches, as he operated at a high level to catch the eye of Premier League outfit Southampton in the summer of 2018. Under Mauricio Pellegrino, Mark Hughes and Ralph Hasenhüttl, Vestergaard developed his reputation as gifted central defender.
His debut season in England’s top-flight saw him help his outfit secure their Premier League status, while 2019/20 resulted in an 11th-placed finish and a debut goal for the Saints against Manchester United.
The central defender’s final full season at Southampton, meanwhile, ended with his former side positioned 15th, alongside a run to the semi-finals of the Emirates FA Cup where they were beaten by eventual winners Leicester City. After signing for the Foxes in August, meanwhile, Jannik swiftly made his debut, coming off the bench in a 1-0 win over Wolves at King Power Stadium on the opening weekend of the 2021/22 season.