Chelsea were football's biggest spenders in the past two transfer windows after forking out over half a billion dollars, so you could be forgiven for thinking that the Premier League giants were going to have a relatively uneventful summer this time around.

However, American co-owner Todd Boehly continued to flex his financial muscle as Chelsea added another star name to their squad after completing the signing of Senegal striker Nicolas Jackson on an eight-year contract from Villarreal.

Chelsea didn't disclose the fee involved but according to multiple media outlets, the Blues will pay around £32 million ($40.4 million) for the 22-year-old, who finished last season by scoring 13 goals in 38 appearances. He is the club's second summer signing after French sensation Christopher Nkunku's arrival from RB Leipzig for £52 million.

"Jackson is a young player with big potential," read a Chelsea statement. "We believe he is ready for this next step in his career and look forward to him working with our new head coach, Mauricio Pochettino, and his Chelsea teammates."

Jackson's deal comes on the day that Moroccan winger Hakim Ziyech's move from Chelsea to Al Nassr collapsed at the last minute after concerns were raised following the discovery of a knee problem during his medical. It's also understood that there was a late disagreement over personal terms.

Despite the dramatic twist, a number of big names left Stamford Bridge over the past few weeks as Chelsea started the overhaul of their squad for next season.

N'Golo Kante, Kalidou Koulibaly and Edouard Mendy have already left for clubs in the Saudi Pro League. Kai Havertz has joined Arsenal, while Manchester City have signed Mateo Kovacic. 

Manchester United have agreed a deal to buy Mason Mount, and Ruben Loftus-Cheek completed a move to AC Milan on Friday.

Chelsea's rebuild will continue in the coming days with their skipper Cesar Azpilicueta close to joining Atletico Madrid. The 33-year-old, who made only 16 starts last season, has won a Champions League and two league titles during his stint in London.

Meanwhile, Liverpool have triggered Dominik Szoboszlai's £60 million release clause with the intention of making the Leipzig talisman their new midfielder.

The Hungary captain had also been linked with Newcastle United, but Liverpool emerged as frontrunners to sign Szoboszlai, who played an instrumental role in leading Leipzig to the German Cup title last season, after meeting with his agents earlier this week.

The 22-year-old playmaker notched 20 goals and 22 assists during his last two seasons in the Bundesliga. He is expected to bolster Liverpool's attacking options after the departures of Alex Oxlade-Chamberlain, Roberto Firmino, Naby Keita and James Milner.