Chelsea also won the League Cup by beating Middlesbrough 2–0 in the final the following year, and Sinclair scored the opening goal in extra time.

Sinclair was appointed as player-manager at Colwyn Bay in February 2013 and was named Conference North Manager of the Month in April and December 2013.

[3] He attended Pimlico School in Westminster and was offered trials at Chelsea, Arsenal and Wimbledon whilst he represented the West London district team.

[5] In April 1991, after a run of four consecutive defeats, Chelsea manager Bobby Campbell decided to blood some youngsters at Luton Town.

[6] Sinclair was chosen out of position at left-back, but impressed on his debut as Chelsea fought back from 3–0 down to draw the match 3–3 despite having ten men for the whole of the second half.

[5] Despite video evidence showing that the "butting" was accidental he was still found guilty by The Football Association and received a nine-match ban and a £600 fine.

[6] Glenn Hoddle was appointed as manager for the 1993–94 season, replacing David Webb, and preferred using a sweeper system which saw Sinclair convert into a central defender.

[6] Chelsea could not prevent United from claiming the league and cup double in a 4–0 defeat, with Sinclair conceding the penalty for a foul on Andrei Kanchelskis in the second-half, which was scored by Eric Cantona to make it 2–0.

However, he made six appearances in the FA Cup and was one of three centre-backs – the others being Frank Leboeuf and Steve Clarke – to start in the 1997 final as they beat Middlesbrough 2–0 to lift the trophy.

On 9 August, he hit the headlines after celebrating a goal against Coventry City by dropping his pants; he later explained he did this in tribute to his newborn daughter.

Sinclair, along with four Chelsea players, had gone on a five-hour drinking binge and had stripped off, swore and vomited in front of American tourists just hours after the September 11 attacks which killed nearly 3,000 people in America.

They then made an immediate return to the top-flight in 2002–03, crowning their maiden season at the Walkers Stadium with a second-place finish in the First Division, Sinclair featuring in 37 games.

In March 2004, Sinclair and his Leicester City teammates, Paul Dickov and Keith Gillespie, were arrested in Spain over sexual assault charges while on a training holiday.

[28] On 24 December, Sinclair signed a new two-year contract extension until June 2007, with "Clarets" manager Steve Cotterill stating that "he has been an integral part of our defence".

[28] On 1 November, he was on the receiving end of alleged racism in a 2–1 win over Millwall, with opposing player Ben May being sent off in the tunnel at half-time for words said to Sinclair.

[28] At the start of the 2006–07 season, with Sinclair's first-team place no longer assured, Steve Cotterill handed over the captaincy to new signing Wayne Thomas.

[36] Sinclair signed a one-year contract with League Two side Lincoln City on 1 July 2008, reuniting with manager Peter Jackson who originally brought him to Huddersfield Town.

[37] Jackson hailed Sinclair's "determination, his personality and his will to win", and said that both Wycombe Wanderers and Brighton & Hove Albion were interested in signing the player.

[38] On 26 March 2009, Sinclair made the surprise move to Wycombe Wanderers on loan from Lincoln City; former Leicester manager Peter Taylor was in charge at Adams Park.

[51] Following on from his impressive form for Chelsea in the 1994–95 season, he was called up by Terry Venables to the England squad for the Umbro Cup final match against Brazil in June 1995.

[53][54] Manager René Simões had called up several English-born players such as Deon Burton, Robbie Earle, Paul Hall, and Fitzroy Simpson in the qualification matches and wanted Sinclair to join the group.

"[51] He was called up to the squad for the 1998 CONCACAF Gold Cup held in February, making his debut in the opening group stage match against Brazil, which finished in a 0–0 draw at the Miami Orange Bowl.

[56] Jamaica were knocked out in the semi-finals due to a 1–0 golden goal defeat to Mexico, and finished in fourth place overall as they lost to Brazil in the third-place play-off match.

[56] In July 2000, the newly appointed Jamaica technical director of football, Clóvis de Oliveira, decided to axe the five based British-based players, including Sinclair, from the upcoming 2002 FIFA World Cup qualifiers for "disciplinary reasons".

[58] He wanted to give the younger players a chance of breaking into the team and wished to focus on his club career with Leicester City, stating that the transatlantic travel could affect his form.

[60] After being appointed player-manager, Sinclair helped save Colwyn Bay from relegation and was named as Conference North Manager of the Month for April 2013 after overseeing six successive victories.

[67] On 5 January 2015, he resigned as manager of Colwyn Bay, a day after a 5–0 defeat to Boston United which left the club 11 points outside the play-off places.

[75] Town lost just two of their first six games of his second spell in charge, but Sinclair left the club permanently on 15 April, just days after stating his intention to stay on at Keys Park for the following season.

[80] He was appointed as the club's head of coaching development five months later, saying that "I see a key part of my role as bridging the gap between the younger players and the first team".

[81] Interim manager Danny Pugh had to start self-isolation after testing positive for COVID-19 on 18 January 2021, leaving Sinclair, Billy Paynter and Anthony Griffith to take over first-team duties in his absence.