WHAT HAPPENED? Chelsea have signed Zakaria from Juventus less than a year after he arrived in Turin from Borussia Monchengladbach. He comes on loan with a reported £30m buy option. Chelsea will cover his full salary this term. THE BIGGER PICTURE: Blues were overrun in midfield during 2-1 loss to Southampton this week, with injuries decimating the position group for Thomas Tuchel. The addition of Zakaria could provide immediate relief at Stamford Bridge. AND WHAT'S MORE: Tuchel has also brought in big-name signings such as Raheem Sterling, Kalidou Koulibaly and Wesley Fofana this summer, but a poor early start to the campaign has created a sour mood in west London despite the spending. STORY IN THREE PHOTOS: Chelsea are going through a tough period. Especially with N'Golo Kante struggling with fitness. So the addition of Zakaria could be a difference maker for Tuchel. WHAT NEXT FOR CHELSEA? Chelsea will meet West Ham this weekend before beginning their Champions League campaign.