Premier League | Table toppers Chelsea strengthen position with 4-2 win over Southampton

Returning to the starting lineup, Hazard opened the scoring for Chelsea in the fifth minute with a low shot. Former Chelsea midfielder Oriol Romeu fired the equalizer for the Saints but the joy was shortlived as Cahill scored to give the Blues a 2-1 lead at half-time.

Chelsea continued their dominance in the second-half as Costa headed home to take the team to 3-1 before scoring his second with a low shot.

Former Chelsea striker Ryan Bertrand was on target for the Saints in the dying seconds but by then Antonio Conte's men assured of a win to mount pressure in second-placed Tottenham Hotspur.

"We've put pressure on Spurs," Hazard told reporters. "It's always good to play before and put pressure on them."

Cahill, meanwhile, called the win a massive step. "It's the first time for a long time we've played before Tottenham," he said.