Costa has recovered from a hamstring injury but Mourinho claims the Spain international may not be ready for the leaders’ Premier League match against Mark Hughes’ side at Stamford Bridge.
“Diego trained yesterday and today with the group,” he said. “He’s not injured. I don’t??know if I start with him or not because, after a muscular injury and two days with the??group, I need to make a decision on him.
“Diego has dedicated himself to recovering, no days off and working hard. At this moment, the muscle is fine.”
Costa was absent for Spain’s 1-0 European Qualifier win over Ukraine and the 2-0 friendly defeat to Netherlands, withdrawing from the squad after suffering a recurrence of a hamstring injury during Chelsea’s 3-2 win at Hull on March 22.
“Only Eden Hazard, Cesc Fabregas and Thibaut Courtois played on Tuesday so the accumulation of fatigue was not so dramatic,” added Mourinho.
However, Mourinho did announce that midfielder John Obi Mikel will not be involved against 10th-placed Stoke.
“We have no injuries but Mikel is not selected,” said the Chelsea boss. “He is fine, he??is working all week with the group. But he’s tired, he’s very tired.”
Chelsea are six points clear of defending champions Manchester City with a game in hand ahead of the Stoke game, and Mourinho spelled out exactly what is required to secure the title.
“We need six victories and one draw from nine matches,” he said. “It’s a good situation for us, one that every club would like to have. If we are champions on the last day, I’m more than happy with that – I’m not thinking about how or when.”
Chelsea are unbeaten at home in 14 home Premier League games this season and, on the threat to that record presented by Stoke, Mourinho said: “Stoke are a difficult team, that’s why they are where they are.
“They know each other very well and they are very stable.”