Diego Costa warned Premier League defenders his best is yet to come after the Chelsea striker maintained his hot streak in Sunday's 1-0 win over West Bromwich Albion.

Costa produced a moment of magic to shatter Albion's stubborn resistence in the 76th minute at Stamford Bridge when the Spain striker robbed Gareth McAuley before firing a fine finish into the far corner.

Costa's 12th league goal in his last 15 appearances lifted Chelsea back to the top of the table, with a three-point advantage over second placed Arsenal.

But ominously for Chelsea's title rivals, the 28-year-old believes he still has room for improvement.

"I am in great form, but not the best," Costa told BT Sport.

Rather than take the spotlight for himself, Costa praised the way Chelsea's defenders had kept their concentration to ensure Albion didn't snatch a shock lead before the Blues finally broke the deadlock.

"The best way to attack is to defend well," he said. "They had a few chances in the beginning, but we are well organised and strong."

Cesc Fabregas came off the bench to play the pass that led to Costa's winner and the former Arsenal midfielder saluted the feisty forward for refusing to let McAuley take the ball away from him.

"It was a good pass but it was all about Diego for the goal, he made the pass special," Fabregas said.

"He fought for the ball. We had to push them but I think the game was asking for a change and I'm glad for that."