The Spain international scored one goal and made another for the Blues in the draw at Stamford Bridge but was forced odd in the 80th minute after receiving lengthy treatment on the pitch.
Costa has scored five goals in five games since Hiddink was appointed as Jose Mourinho’s successor on an interim basis last month.
And Hiddink revealed after the game that Chelsea were waiting to discover the results of a scan after Costa was sent to hospital after the dramatic draw in west London.
Speaking at his post-match news conference at Stamford Bridge, Hiddink said: “He’s in hospital and they will check with a scan. We don’t know the results yet, I hope it’s not too bad.
“It’s on his shin. We hope Diego will come out of the hospital in good health. He was in a lot of pain.”
Saturday’s draw with Everton left Chelsea in 14th place in the Premier League table and just six points above the relegation zone. The Blues have only won three of their last 10 top-flight games.
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