Diego Costa focused on his strengths - Chelsea boss Guus Hiddink

LONDON -- Guus Hiddink hailed the renewed focus of Diego Costa after he scored twice to earn Chelsea a 2-2 draw with in-form Watford at Stamford Bridge.

Costa opened the scoring on 32 minutes with a clinical volley from close range and, after Troy Deeney and Odion Ighalo put Watford on course for victory at the home of the Premier League champions, it was the Spain international who stepped up again to clinically dispatch a Willian through pass and pull Chelsea level.

A late Oscar slip from the penalty spot denied Hiddink a win on his return to Stamford Bridge as interim manager, but afterwards the Dutchman insisted he was pleased with the reaction of his players and particularly of Costa, who was booed by Chelsea supporters when substituted against Sunderland and had scored just four goals in his previous 21 club appearances.

"He focused himself where he's good, and then he's very dangerous," Hiddink said, having challenged Costa to improve his focus during his prematch news conference on Wednesday. "That's important, not wasting extra energy where you shouldn't waste it. I think he did that perfectly with two goals.

"His reaction was very good. When he was booed, right or wrong, when he was substituted by Steve Holland [against Sunderland], he had a very good reaction. He is a very good professional and it made him think 'How should I go on?' and he showed that."

When asked what he had done differently with Costa in his first week of training, Hiddink replied: "Nothing! Don't overestimate the influence of managers. You try to give some people the focus, and that's not big words. Sometimes you go in training and say 'focus on what you have to do' in your team meetings, in the sessions, etc.

"When everyone knows what he is capable of and knows he must not go into whatever the trap might be, then you focus on your first job. He's good at it and he showed it with two terrific goals."

Optimism over Costa's improvement was tempered by a fifth Premier League booking of the season that means he will miss Chelsea's clash with Manchester United at Old Trafford on Monday, and Hiddink admits his striker's suspension has come at a bad time.

"He is out, which means we have to think how to solve that problem," Hiddink added of Costa. "It's a pity because now he's going into a good performance, but we have to solve that problem in 48 hours."

Hiddink should have been celebrating a win on his return to the Bridge after Valon Behrami recklessly upended Blues substitute Eden Hazard in the area 10 minutes from the end.

But Oscar slipped as he ran up to the ball and ballooned his penalty over the crossbar, leaving Hiddink to quip: "He must have had slicks on, when he should have had normal tyres on."

Watford arrived in west London looking for a fifth straight win and manager Quique Sanchez Flores, who played under Hiddink at Valencia, was happy to come away with a draw.

"I'm completely satisfied," he said. "Chelsea were really motivated, very strong, very aggressive, so I am happy with the performance and really happy with the result.

"It's always difficult to play against Chelsea. They are an amazing team. And Hiddink is an amazing coach.

"It was funny being in the dug-out next to him. In the second half he told [Branislav] Ivanovic -- who played in my position -- to do something and then said 'but not like Sanchez Flores!'