Thomas Tuchel took over at Chelsea in January and instantly became a success at the club, moving the club from ninth to a top four finish and reaching two finals, the FA Cup and the UEFA Champions League; he lost the former but won the latter, all within five months.
His immediate success has made the Blues bosses to back him with more funds despite taking over a squad that spent over £200m last season. Romelu Lukaku was re-signed from Inter Milan for £97.5m to bolster his attacking options and the club are willing to put down more funds.
Sevilla's Jules Koundé who the club chased unsuccessfully in the summer, Juventus' Matthijs De Ligt and Monaco's Aurelien Tchouameni are on the Blues radar for the January transfer window as reinforcement in defence and midfield.
Asides transfers, Chelsea have two contract renewal issues to tackle, Antonio Rudiger goes out of contract at the end of the season and is yet to renew while talks with Andreas Christensen also broke down. As much as reinforcements are needed, extending this contracts are also necessary.