Chelsea boss Jose Mourinho has admitted that Oscar has been struggling with fatigue and the recent bad weather in England.
The Brazilian play-maker was in instrumental form at the start of the season, he even forced last year's player of the season, Juan Mata, out of the team, which led to the Spaniard's exit to Manchester United in January.
However he has tailed off a little recently and has only played the full 90 minutes on one occasion so far in 2014. Meanwhile the likes of Willian and Eden Hazard have been performing regularly.
Having moved from the sunnier climate of Brazil in 2012, the recent downpours are somewhat alien conditions to the 28-cap international.
Mourinho claims he isn't concerned too much with the 22-year-old's quiet patch though.
"Maybe in the last couple of matches he was not the same, because in the beginning of the season he was the best player in the team," Mourinho said.
"He was the player that was really making the difference in the first three, four months of competition.
"In this moment he's not being a match-winner, he's not scoring goals, but he's not playing bad. Not real problems.
"The talent is there all the time, but the physical top condition to express the quality he has is not always there.
"We have to take care of him. He's a young boy. He's not a natural physically strong man, suffers with the accumulation of matches, suffers with the difficult weather we had."
Chelsea, with Oscar in the team, host Everton this afternoon with the chance to move four points clear at the top of the Premier League.