Hobbs is the youngest-ever player to feature for Lincoln City in the Football League. He was 16 years and 149 days when he came on as substitute against Bristol Rovers on 15 January 2005. The central defender joined the Reds from Lincoln City in August 2005 following a successful trial spell at Melwood and became the captain of the reserves. Because of the long-term injury to Agger, Hobbs got an opportunity when he came on as a late substitute for Lucas in the League Cup at Reading in September 2007. He played the whole 90 minutes of the next round against Cardiff and made his full League debut five weeks later away to Reading. The arrival of Martin Skrtel diminished Hobbs' chances of a long run in the first team. So it wasn't a major surprise that on 24 January 2008 Liverpool loaned him to Scunthorpe United in the Championship for the rest of the season. Hobbs was loaned to Leicester City for the 2008/09 season and performed so well his move was made permanent.
Hobbs played in 44 Championship matches for Leicester in the 2009/10 season as the Foxes reached the play-offs. Hobbs was honoured by being made captain for both legs of the semi-final with Cardiff City but the Welsh club progressed on penalties to leave Leicester's Player of the Year devastated that his dreams were crushed at the penultimate stage of the season.
Leicester signed a number of new defenders for the 2010/11 season which meant that Hobbs was no longer certain of his place in the team, surprisingly considering his player award from the previous campaign. In February 2011 he made a loan-move to Hull City and appeared in 13 Championship matches for the Tigers before signing a permanent three-year deal. Hobbs was named captain in Nicky Barmby's side and was an exceptional performer for the club, but ruptured his anterior cruciate ligament in April 2012.
Hobbs returned to action after recovering from a serious injury and played in twenty-two Championship matches in 2012/13 as Hull City made a return to the Premier League after an absence of three years. The defender moved to Nottingham Forest on loan from Hull City for the whole of the 2013/14 season with part of the agreement being that after this loan-spell was over he would then sign a two-year contract with the Nottingham club. Hobbs returned briefly to Hull in January 2014 but then signed a four-and-half-year permanent deal with Forest on the final day of the mid-season transfer-window. The defender made 27 league appearances for Forest in 2013/14 as the Nottingham club finished the season in eleventh place, several points and positions behind the play-off places. he also appeared once each in the League Cup and FA Cup. Jack's only goal of the season was the only goal of the East Midlands derby against Derby County at the City Ground in September. In 2015/16 he was a regular in the first half of the season but missed the second half due to a back problem which required surgery. Over the next two seasons he made only fourteen appearances due to a succession of injuries.
After being released at the end of 2017/18 he joined Bolton Wanderers, who he was unable to help void the drop to League One. Bolton's financial problems meant he was released, but when a takeover was completed he re-joined them at the end of August 2019, facing an uphill struggle to avoid a second successive relegation due to a points deduction. Bolton were cast adrift at the bottom of League One when the season was suspended in March due to COVID 19. They were relegated on a points per game formula when the season was terminated early but he was not offered a new contract after struggling with a back injury that limited him to eleven league games. Hobbs went on to confirm that his playing days were over and in September 2021 he returned to his fist club Lincoln City in an academy coaching role.