Diego Costa
Chelsea manager Jose Mourinho looks on as Diego Costa sustains an injury during the Blues' Premier League clash at Hull City on SundayReuters

Chelsea boss Jose Mourinho has confirmed that Diego Costa has sustained a hamstring injury and is unlikely to be available during Spain's 2016 Euro qualifying clash against Ukraine on Friday.

The 26-year-old striker, who scored his side's second goal during the Blues 3-2 Premier League win at Hull City on Sunday, was replaced by Loic Remy after picking an injury in the 75th minute of the game.

And Mourinho has now confirmed that the Spain striker was substituted due to him suffering from a hamstring problem.

"It's a hamstring injury," the Portuguese told Chelsea's official website after the match. "When a striker is playing, the team needs a goal to win the game and he says it's over for him, it's over."

Costa has had a lot of problems with his hamstring in the past, with the striker not being able to play for long during last season's Champions League final between Atletico Madrid and Real Madrid.

He also suffered from another hamstring injury earlier this season following his £32 switch from Atletico Madrid to Chelsea last summer.

Although Mourinho admits that the Brazil-born striker's hamstring is "not strong", he insists that Costa "works hard" in training to "compensate" for that weakness.

"He has this problem since he tried to play the Champions League final with Atletico and was injured again and again," said Mourinho. "He has this fragility. We know his hamstring is not strong."

"He works hard in the week to compensate for the weakness he has there but the injury can come."

The former Real Madrid boss went on to reveal that the club doctor has advised against Costa undergoing a surgery for his persistent hamstring problems.

"Dr [Paco] Biosca is against knives, against surgery," Mourinho added. "He's all in favour of conservative work and collective work between medical department and fitness technical staff. And this is the direction, we believe."

Costa replacement Remy scored the winner for Chelsea against Hull City on Sunday, and Mourinho admits that the French striker deserves more playing time than he has got this season.

"Every time he plays he's there," said Mourinho. "He probably deserves more than I gave him. There are not many times when a coach can feel he owes something to a player and with Remy that's the case. I think I owe him something. Every time he plays he gave us a lot. I am happy for him. He never complained."