DIEGO COSTA has shaken off his nagging injury problems ahead of a fixture marathon that Jose Mourinho knows could take its toll on the Chelsea star.

The 26-year-old striker has netted 10 goals so far this season despite battling hamstring and groin issues.

But missing Spain's fixtures this week gave him the chance to make a full recovery.

It is a timely boost ahead of Chelsea's run of eight matches in the next 24 days.

Mourinho said: "We're going into a period that is new for him.

"I always think the pre-Christmas period is more difficult for players doing it for the first time in their careers.

"English players, or those who have been here for many years, are more physically and mentally prepared to cope with that incredible marathon of football.

"In the past two weeks Diego was working many, many hours a day with our physio. At this moment we feel he's free of his old injury."

A fully fit Costa is a worrying prospect for Barclay's Premier League rivals, starting with today's opponents West Bromwich Albion.

Chelsea go into the match well clear at the top after garnering 29 points from 11 games.

Their form has led one bookmaker to pay out on them winning the title but Mourinho scoffed at suggestions the league race was all but over.

He said: "If we lose games, and I believe we will, it won't be because of complacency.

"It will be because football is football."