Ref Watch: Chelsea's Season  (Sky Sports)

We round up the controversial calls involving Premier League champions Chelsea from Ref Watch over the past 12 months.

Former top flight referee Dermot Gallagher has been running the rule over the key decisions in the Premier League on Sky Sports News HQ every Monday, but how many have gone for and against the Blues?

Here, we take a look at the most contentious and most important calls of the 2016/17 season. Tomorrow, we continue with Liverpool...

Watford 1-2 Chelsea, August 20

INCIDENT: Diego Costa avoids a second yellow for 'simulation'. Having already been booked, Costa goes over on the edge of the box following the slightest of challenges from Watford defender Miguel Britos. However, the referee decides the Chelsea striker did not dive. Costa then goes on to score the winning goal.

DERMOT'S VERDICT: Correct decision - The law says 'deceiving the referee into give a free kick or penalty'. The referee has to decide whether he's made a deliberate simulation to win a free kick or penalty. In the case where a player is on a yellow card he must be 100 per cent sure to send him off. If he has any doubt whatsoever he's got to back off and that's what I think happened here. The referee wasn't sure whether Costa actually initiated contact or the contact was initiated on him and he chose not give a red card. I think that's absolutely right because looking at that I think it is simulation, but if I was going to send him off I would want to be absolutely sure.

Swansea City 2-2 Chelsea, September 11

INCIDENT: Gary Cahill is tackled from behind by Leroy Fer, who then goes through to score. Chelsea's central defender loses the ball to the Dutchman in the build-up to Swansea's second goal, with referee Andre Marriner allowing play to continue.

DERMOT'S VERDICT: Incorrect decision - The referee has gone to what is a natural position, expecting the ball to be cleared up field. It is played across the park, Cahill has dwelt on the ball and he thinks Leroy Fer has poked the ball between his legs from where he is. But he has not and he [Marriner] has completely misread it, so it is a foul.

Chelsea 4-0 Manchester United, October 23

INCIDENT: David Luiz is booked for a tackle on Marouane Fellaini. With Chelsea winning 2-0, Luiz is only shown yellow even though the challenge was with his studs, catching Fellaini on his knee.

DERMOT'S VERDICT: Incorrect decision - If the referee sees the angle we have seen, he would definitely show a red card because he has shown six studs, caught him high on the knee and the ball has gone. Martin Atkinson is the other side and has seen the high boot. He thought he caught him, but didn't see the seriousness. I thought it was a red card. If you go in that high with studs showing, you run that risk.

Manchester City 1-3 Chelsea, December 3

INCIDENT: With the score goalless, Chelsea defender David Luiz appears to block Sergio Aguero as the Manchester City striker attempts to break through on goal. Referee Anthony Taylor puts his whistle to his lips, but instead decides against awarding a free-kick despite the apparent foul that denied a goalscoring opportunity and would have seen Luiz sent off.

DERMOT'S VERDICT: Incorrect decision - David Luiz knows what he's doing, the ball is within possession of Aguero once he gets past. The ball then only runs away because he stops him. I think it's a foul and a red card.

You see Anthony make that decision in his head, then he takes his whistle away. All I can think is he's had some input from one of his assistants to say it's not [a foul] from their angle. That does surprise me because, having seen the incident, if I was the referee you'd have to sell me a big, big deal for me to change my mind like that.

Manchester City 1-3 Chelsea, December 3

INCIDENT: Diego Costa scores the equalising goal for Chelsea despite appearing to use his arm in the build-up. The Chelsea striker isn't penalised, beats Nicolas Otamendi and goes on to find the back of the net. The goal is allowed to stand and the Blues go on to win the game.

DERMOT'S VERDICT: Correct decision - I think he's taking it on his chest. His arm is out, but for balance. Otamendi appeals at the end but his first priority is to go after the ball. He doesn't even stop to think he's handled the ball, and for me he's taken it well and it was a good goal.

Chelsea 2-0 Hull, January 22

INCIDENT: With the score at 1-0 to Chelsea in the second half, Marcos Alonso kicks the back of Abel Hernandez's heel in the penalty area after miscuing a clearance. No penalty is given by the officials, despite the incident occurring in front of the linesman.

DERMOT'S VERDICT: Alonso is lucky. Very, very lucky. And I think he knows it too, his reaction tells it. It just wasn't a wise decision to make. He has trod on his heel, and again it's one that I thought the assistant could have seen, rather than the referee.

Liverpool 1-1 Chelsea, January 31

INCIDENT: Jurgen Klopp escaped punishment for shouting in Neil Swarbrick's face following Mark Clattenburg's decision to award Chelsea a penalty after Joel Matip's second-half challenge on Diego Costa. Klopp afterwards revealed that Swarbrick congratulated him on his 'passion' once he had received an apology from the Reds manager.

Manchester United boss Jose Mourinho took aim at Klopp and accused Premier League referees of favouring the German after he was told to sit down for a similar outburst during Manchester United's goalless draw with Hull the following day.

DERMOT'S VERDICT: Incorrect decision - The fourth official who spoke to Jose Mourinho acted within the guidelines and the procedures he was given at the start of the season.

The problem emanates from the fact that, when you watch Jurgen Klopp on Tuesday night, for me in view of the procedures, that's totally unacceptable. It was something that had to be dealt with and it wasn't dealt with. I feel that Klopp should have been removed without doubt.

Chelsea 3-1 Arsenal, February 4

INCIDENT: Marcos Alonso and Arsenal defender Hector Bellerin both jumped to attack the ball in the six-yard box with the Chelsea man winning the battle and heading home for 1-0. However, as he jumped, he caught Bellerin with his arm, knocking the full-back to the ground. Arsene Wenger called it a "100 per cent foul." The goal stood.

DERMOT'S VERDICT: Correct decision - They've both jumped with their arms in the air and both are focused on the ball. Alonso never looks at Bellerin once. It was natural contact. It would have been more of a surprise if it had been disallowed.

Manchester United 2-0 Chelsea, April 16

INCIDENT: Ander Herrera appears to handle Nemanja Matic's pass. The United midfielder blocks the Serb's through ball with his hand, but referee Bobby Madley deems it accidental, with the home side then going on to open the scoring.

DERMOT'S VERDICT: Incorrect decision - I thought it was (handball), but what I would say in defence of the referee, if you watch he has a great view, he makes a decision and clearly says: 'No'. So although I think he has got it wrong, I will applaud the referee for not hiding behind the fact like there was a player in my way, I was at the wrong angle. All I can presume is that he has judged a) the ball has come too close to him and his arm was already there and b) it has hit him too fast.

The amazing thing about it is as a consequence the ball quickly goes to Marcus Rashford and he scores, so it is a massive, massive incident and that is how fine a line referees tread. If that ball had just gone out for a throw in, we would not be talking about it.