The 24-year-old joined the Bundesliga club after an unsuccessful stint at rivals Bayern Munich for £7million in 2008 and was part of Germany's World Cup squad that finished in third place.
Jansen scored the opener in the Germans' 3-2 win over Uruguay and has reportedly caught the eye of Liverpool boss Roy Hodgson following his performances for Hamburg.
The Reds are looking for a left-back after selling Emiliano Insua to Fiorentina and releasing Fabio Aurelio, meaning they have no senior cover for the position.
Hodgson has been linked with moves for Paul Konchesky, Maynor Figueroa and Carlos Salcido, but so far none have come to fruition.
Jansen's ability to play as a left winger could be a reason behind a possible bid, but agent Gerd vom Bruch stated that the player was committed to his current club.
"The interest in him is a credit to Marcell," he told the Hamburger Morgenpost newspaper.
"But he is under contract with Hamburger SV and will be respecting this."