Grimsby Town

Lester started his career with Grimsby Town and signed his first professional contract in 1994. He was nurtured into a first team role at Grimsby by manager Alan Buckley and his assistant John Cockerill. After a brief loan spell with Doncaster Rovers in which he played 11 games (5 in the starting lineup) and scored one goal, Lester became a regular at Blundell Park. During his time there he formed notable strike partnerships with Clive Mendonca, Steve Livingstone, Lee Ashcroft and Jamie Forrester. It was during the 1997–1998 season that he had arguably his best season with Grimsby. He was a regular fixture in the first team and helped the club succeed in an impressive double final win at Wembley Stadium. The Mariners defeated AFC Bournemouth in the Football League Trophy (although Lester was suspended for the final)^[2] before beating Northampton Town in the Division Two play-off Final a few weeks later.^[3] Lester stayed with Grimsby until midway through the 1999–2000 season when he was controversially sold just after the turn of the millennium. He made 133 league appearances and scored 17 league goals in his time with The Mariners, and is still a popular figure at the club.

Nottingham Forest

David Platt signed Lester for Nottingham Forest in February 2000 for £300,000, just three weeks after he led the Grimsby attack beating Forest 4–3 in the League; it was from that game that Platt became interested in signing the player. It took some time for Lester to settle in at the City Ground but when Platt left the club, new manager Paul Hart moved him to an attacking midfield role where he flourished, making over 70 starts and scoring 24 goals. In 2003, he was released by Hart in an attempt to reduce debts.

Sheffield United

After an unsuccessful trial at Sheffield Wednesday, he was signed by Wednesday’s bitter rivals Sheffield United at the start of the 2003–4 season. Lester played alongside Steve Kabba amongst others at Bramall Lane. He remained a first choice striker at the club for the entire season and made 50 appearances for United until his exit in November 2004.

Return to Forest

Lester was offered the chance to return to Forest and he was re-signed by Joe Kinnear in 2004 for £50,000. He scored in his first game but in his third start damaged knee ligaments which kept him out of action for almost 9 months. He went on to play 88 games in this second spell. Then after Nottingham Forest failed win promotion in the 2006–07 season, he was released by manager Colin Calderwood.^[4]

Chesterfield

In June 2007 he signed for Chesterfield on a 3-year contract.^[5] He finished the 2007–08 season as Chesterfield's top scorer, with 25 goals in all competitions. This tally made him 3rd top scorer in League Two, with 23 goals in the league, 6 behind Aaron McLean of Peterborough United. That season he also became the fastest post-war Chesterfield player to 20 goals in a season, getting his 20th (and 100th career goal) live on TV against Hereford United. He finished the season third in England on goal to game ratio, behind Cristiano Ronaldo and Fernando Torres. Lester scored his 100th League career goal in the 2–1 win over Exeter City on 28 January 2009. He also set a club record in becoming the first striker at the club to score 20 goals in consecutive seasons for 82 years. Despite scoring fewer goals than in his first season at Chesterfield, he finished the 2008–9 term as joint-top scorer for League Two, with 20 League goals.

In the 2010–11 season Lester scored 17 goals in 43 games (all in home games) as Chesterfield won Football League Two. Later going on to sign a new 2-year contract, keeping him at the club until June 2013. Lester suffered a broken arm against Leyton Orient in September 2011 which kept him out of the side for three months. Lacking both Jack and injured goalkeeper Tommy Lee, Chesterfield's results suffered and the team slumped to the foot of the division. Lester returned to the team in late December but was suspended and missed three further matches after the referee in the home game against Walsall watched recorded footage from the game and saw him strike an opponent. On 30 January 2012 Jack scored the late winning goal at Boundary Park against Oldham Athletic which ensured that Chesterfield reached the final of the Football League Trophy at Wembley, on a 3–1 aggregate score.

In his final season for Chesterfield, 2012–13, Lester played the majority of his games from the substitutes bench. He made only 11 starts despite figuring in 38 games in all competitions. Regardless of this his score rate is still impressive, having bagged 11 goals from just 1,454 minutes of football (the equivalent of just over 16 full games).^[6] Jack played his last game for Chesterfield, and his last game in professional football on 27 April 2013. He scored twice as The Spireites won 4–0 in a game that was a "fitting send off for a player who will forever be remembered by the Chesterfield faithful".^[7] His legendary status is regularly referred to by the club and fans^[8] and in August 2013, Chesterfield announced that the number worn by Lester throughout his time with the club, 14, would be retired in his honour.^[9]

Gateshead

On 3 February 2014, Lester came out of retirement, signing for Conference Premier side Gateshead on non-contract terms.^[10] He made his Gateshead debut on 25 February as a second-half substitute in a 2–0 defeat at Welling United.^[11] He made his first start and scored his first goal for Gateshead on 22 March 2014 in a 3–1 win against Lincoln City.^[12] He was part of the Gateshead side that pushed for promotion to the Football League and after defeating former side Grimsby Town in the play-off semi-final, Gateshead were eventually beaten in the final at Wembley Stadium by Cambridge United. Lester came on as a 69th-minute substitute and scored in the 80th minute but the club went on to lose 2–1. The game marked Lester's final appearance before retiring.^[13] At the end of the season in accordance with his decision to retire, Lester was released by Gateshead following the end of his contract.^[14]