Chelsea manager Jose Mourinho blames Spain coach Vicente del Bosque for Diego Costa's recent injury troubles.
Costa scored nine times in seven matches in a prolific start to his Stamford Bridge career, but he has missed their last three fixtures with a hamstring problem.
However, the 26-year-old is now back in full training and could return in Saturday's west London derby at home to QPR in the Premier League.
The Spain international was suffering with a cold last week as well, but Mourinho says it was injury that forced him out of Sunday's 1-1 draw at Manchester United and he feels the problem was exacerbated by del Bosque playing Costa in back-to-back internationals with Luxembourg and Slovakia at the start of the month.
"The virus is fine," Mourinho said.
"It was hard, he had to go to the hospital and obviously it doesn't help him to recover from his injury. But he didn't play on Sunday because of the injury, not because of the virus.
"Diego has the hamstring (problem) because he played two matches in three days when he was not with us."
Live Capital One Cup Football
When asked whether he hoped Costa's injury problems were now over, Mourinho replied: "But he still has (to play for) the national team in November!"
Costa will be missing when Chelsea take on Shrewsbury in the fourth round of the Capital One Cup on Tuesday night and Mourinho is taking the League Two side seriously.
"You can say that Shrewsbury in the Capital One Cup is a friendly, but we have to play the match and respect the match," Mourinho added.
"They are doing very well in their league, they are did very well against superior teams (Norwich, Blackpool and Leicester) in the Capital One Cup.
"It is a big day for them and we know it is going to be difficult for us. And because we have so many injured players, it is even more difficult."
Watch Chelsea's trip to Shrewsbury in the Capital One Cup live on Sky Sports 1 HD on Tuesday from 7:30pm.