The Blues reportedly made a move for Sule during the summer but the centre-half decided to stick with Hoffenheim.
Chelsea boss Antonio Conte is eager to add to his defensive options during the January transfer window and is believed to be ready to make a fresh move for the 21-year-old, who made his Germany debut earlier this year.
However, the Stamford Bridge side could face a battle to land Sule, who is under contract until 2019 with the Bundesliga club, as ESPN say Bayern Munich are also keen and may launch a rival bid.
Darren Ferguson declared his delight at a 'big win' for Doncaster after they saw off Bradford 2-0.
Doncaster took a major step towards securing their Sky Bet League One survival by beating Bradford 2-0.
Southampton manager Mark Hughes was delighted to see his new side reach the FA Cup semi-finals but also warned that the Premier League remains a concern.
Borussia Dortmund winger Andre Schurrle was delighted with the team's hard-fought 1-0 Bundesliga victory over Hannover 96 on Sunday afternoon.