Westbrooke began his career in the academy at Chelsea, before moving to West London neighbours Brentford in 2011 and signing scholarship forms at the end of the 2012–13 season. By the completion of his scholarship in April 2015, he had made 55 appearances and scored four goals for the youth team, in addition to scoring two goals in eight matches for the Development Squad during the 2014–15 season. Westbrooke signed a one-year Development Squad contract for the 2015–16 season and by November 2015 he had impressed sufficiently to sign a one-year extension. He finished 2015–16 with 23 appearances and one goal. Westbrooke was named captain of the new B team for the 2016–17 season and signed a new one-year contract on 17 February 2017. He topped the B team's appearance-chart during the 2016–17 season, having made 38 appearances and scored six goals. Westbrooke was called into the first team squad for the final two matches of the 2016–17 season and made his debut in the West London derby with Fulham as a 76th-minute substitute for Konstantin Kerschbaumer on 29 April 2017. Westbrooke was named as the club's 2016–17 B Team Players' Player of the Year on 7 May. Mounting injuries led to his inclusion on the bench for a league match versus Ipswich Town on 19 August 2017, but he remained an unused substitute during the 2–0 defeat. Westbrooke subsequently spent much of the first half of the 2017–18 season away on loan and after his return on 10 January 2018, he spent the remainder of the campaign with the B team. He departed Griffin Park on 10 May 2018, having made just one first team appearance.
On 1 September 2017, Westbrooke joined National League strugglers Solihull Moors on a one-month youth loan. He made his debut the following day as a 69th-minute substitute for Darren Carter in a 1–0 defeat to Aldershot Town. Westbrooke made his first start for the club in the following match versus Chester and assisted Oladapo Afolayan for the Moors' first goal, but received the first red card of his career after 74 minutes of the 2–0 victory. After serving his suspension, Westbrooke failed to make any further appearances before his loan expired in late September.
On 11 October 2017, Westbrooke joined National League club Leyton Orient on a 93-day loan. He made 8 appearances before dropping out of the squad entirely in mid-December and he returned to Brentford when his loan expired on 10 January 2018.
Coventry City
On 10 May 2018, Westbrooke joined Coventry City on a two-year contract on a free transfer, with the option of a further year, effective 1 July 2018. The club's victory in the 2018 League Two play-off Final, after the announcement of his transfer, meant that he began his time with the club in League One. After a substitute appearance in an EFL Trophy group stage match, Westbrooke made his full debut for the club with a start in a 1–0 win over Southend United on 29 December 2018. He had a short run in the team in late-January and early-February 2019 and finished the 2018–19 season with eight appearances. Westbrooke broke into the team and made 33 appearances and scored four goals during a shortened2019–20 season, which ended with promotion to the Championship as League One champions.
