Blues signed Croatia Under-21s captain Ivan Sunjic from Dinamo Zagreb for an undisclosed fee on a five-year contract.
Prior to moving to the St. Andrew's Trillion Trophy Stadium, Sunjic was being eyed by significant mainland European clubs as well as others in England.
A central midfielder, he is positionally astute, competitive and able to force or win back possession outright and he is comfortable in possession, able to hit a variety of passes.
He is seen by Pep Clotet as the ideal kind of player to help Blues transition in style and formation.
Born in the Bosnian city of Zenica, Sunjic's talent was recognised at a young age when he was selected to represent Croatia Under-16s in a friendly against Italy in April 2012.
That was the start of regular international recognition for the midfielder, including involvement in the Under-17s World Cup tournament in 2013.
Sunjic's domestic career began with Croatian top-flight club Dinamo, where he made his debut in the senior side as a 17-year-old in May 2014. Later in the same year, he captained his country for the first time in an Under-19s fixture.
Sunjic skippered Dinamo's second team during the first half of the 2015/16 season before transferring to fellow Zagreb-based outfit NK Lokomotiva, where he went straight into the first team.
He helped Lokomotiva finish fourth in the Croatian top division and qualify for the 2016/17 Europa League. After making it through three preliminary rounds, hopes of reaching the group stages were dashed in the final qualifier, beaten over two legs by Belgian side Genk, with the teenager playing the full 180 minutes.
The summer of 2017 was a significant one for the then-20-year-old as he earned his first, and to-date only, full international cap, playing all 90 minutes as Croatia beat Mexico 2-1 in a post-season friendly.
Sunjic featured regularly for Lokomotiva over two seasons, given the captaincy in the second of those campaigns. His performances earned him a return to reigning Croatian champions Dinamo in February 2018. In that same season, he was also the regular skipper of his country's Under-21s side.
The 2018/19 season was a memorable one for the midfielder as he played five Champions League qualifying games, as well as chalking up eight more Europa League appearances, scoring in a 4-1 win over Fenerbahce, as Nenad Bjelica's side reached the last 16, finally knocked out by Portuguese giants Benfica. Dinamo enjoyed success in domestic competition though, winning the Croatian league and reaching the cup final.