Chelsea lead Schalke 04 1-0 at half time of their Champions League Group G game thanks to Cesc Fabregas's hotly-disputed 11th-minute goal.
Didier Drogba - who is starting his first game in Chelsea colours since the 2012 Champions League final - wasted no time in stamping his presence on the game as he laid the ball into the feet of Ramires in the ninth minute, but the Brazilian midfielder couldn't get any power in his left-footed shot.
Just two minutes later, Chelsea went ahead in controversial fashion as Fabregas netted his first goal for the club.
The Spanish midfielder seemed to catch Max Meyer with a late challenge, but when no foul was given, Eden Hazard advanced on the Schalke defence and cleverly backheeled the ball into the path of Fabregas, who arrived from the left flank to place a shot underneath the reach of Ralf Fahrmann.
Schalke's protests continued long after the goal and Klaas Jan Huntelaar was shown a yellow card for dissent.
Hazard continued to be a menace and saw a shot blocked in the 19th minute before Drogba and then Nemanja Matic both came close to connecting with efforts.
Schalke's first sight of goal came in the 20th minute, when Sidney Sam tested Thibaut Courtois from 20 yards, but the Belgian stopper was equal to the winger's strike.
Kevin Prince-Boateng then became involved in the thick of the action as he saw two goalbound volleys blocked before cynically fouling Hazard as Chelsea tried to break, which earned him a booking.
Chelsea should have put themselves out of sight by the time the half-time whistle blew, but Drogba guided a free header straight at Fahrmann before Fabregas blazed a simple chance high over the bar.
Courtois made a strong save on the stroke of half time to push away a vicious strike by Boateng, and Julian Draxler came within inches of levelling for the visitors after nimble footwork inside the area.