Jonathan Leko joined Blues from West Bromwich Albion on 28 August 2020 for an undisclosed fee.
The forward penned a three-year contract with Blues, who beat off the attentions of several clubs for his signature.
Born in the Democratic Republic of Congo capital Kinshasa, Leko grew up in England from the age of eight.
At the age of 11 he joined West Brom's youth set-up and progressed through the age groups.
His first senior start for the Baggies came on 23 September 2015, when he came off the subs' bench in a League Cup defeat to Norwich City.
He made his Premier League bow for Albion at the tender age of just 16 years and 344 days against Sunderland, as he again came off the bench.
His displays during the 2015/16 campaign saw him recognised with West Brom's Young Player of the Season award.
In August 2017 Leko was loaned to Championship side Bristol City where he made 11 appearances for The Robins before being recalled by his home club during the 2018 January transfer window.
The following August he was loaned out for a second time to Charlton Athletic, but having made 21 appearances and scored five times, his stay was cut short after he suffered an ACL injury against QPR in December 2019, which saw him sidelined for the remainder of the season.
During his time at the Hawthorns Leko made 23 First Team appearances for the Baggies and scored just once, although the majority of his games were as a winger.