LONDON - As Jose Mourinho returns to his Portuguese footballing roots, the Chelsea manager may have to decide which backup marksman he trusts most to shoot down his old employers at Sporting Lisbon.

They meet in a Champions League fixture today.

In his perfect world, Mourinho would turn to his most ruthless hit man Diego Costa to down the club that gave his fledgling coaching career a boost two decades ago by letting him act as manager Bobby Robson's interpreter.

Instead, Costa's continuing hamstring fragility means that, while Mourinho insists he still hopes to start him, he is more likely to have to choose instead between Didier Drogba and Loic Remy to revitalise Chelsea's campaign after their disappointing opening Group G draw with Schalke.

Winning at his old stomping ground will be no easy task for Mourinho, given that Sporting will be protecting a four-year, 16-match unbeaten record, including 13 wins, in European competition at the Alvalade Stadium.

The presence of Costa, whose sensational start to his English career saw him net his eighth goal in six Premier League games in the 3-0 win over Aston Villa on Saturday, could prove the key.

Mourinho reiterated how the 25-year-old's continuing problem with his left hamstring means he can hardly train between games.

"He cannot be on top of his game. He's doing almost nothing in training. He's just resting and recovering from the tight muscle he has. I want to [select him]. Let's see what happens."

Sporting started their first Champions League campaign for five years with a 1-1 draw away at Maribor, leaving the group level.

Under new coach Marco Silva they are unbeaten in all competitions this season, although five of those games have ended as 1-1 draws.

"It will be a good game and we want to give a good impression of our team, which is on the up," said Silva, after another of those 1-1 draws with Porto at the weekend.