Cardiff manager Neil Warnock branded Premier League officials the "worst in the world" after Chelsea capitalised on a refereeing blunder to produce a dramatic 2-1 comeback win.
Chelsea were 1-0 down with six minutes left when Cesar Azpilicueta, who was standing two yards offside, met Marcos Alonso's flick-on to head home the equaliser.
Ruben Loftus-Cheek punished Cardiff further in stoppage time, leaving Cardiff to count the cost of assistant referee Eddie Smart's failure to spot that Azpilicueta was clearly offside.
Warnock also felt that Cardiff should have had two penalties, both for Chelsea players holding Sean Morrison's shirt at set-pieces.
Antonio Rudiger, Warnock added, should also have been sent off for dragging down Kenneth Zohore with the score at 1-1 and the Cardiff substitute through on goal. Rudiger was booked by referee Craig Pawson.
"It's almost like it's not who you play, it's who you get to referee and who is going to have a flag in their hand nowadays, it's just as important," Warnock told Sky Sports.
"The best league in the world and probably the worst officials at the minute.
"He (Smart) is saying that Willian blocked his view, but it wasn't a six inches one. Either side you should be able to see he's two yards offside.
"It's soul-destroying really. I can understand why the lads are down."
Cardiff took the lead against lacklustre Chelsea in the first minute of the second half.
Victor Camarasa struck a splendid volley and Cardiff, who are 18th and in the final relegation place, looked as if they would cut the five-point gap on Brighton, Burnley and Southampton above them.
"If I was a Burnley, Southampton or Brighton fan it's the best thing that could have ever happened," Warnock said.
"It's knocked our lads down, they are flat.
"We've worked on things for the last three weeks and one of them is coming out at corner kicks and leaving a man in.
"The lads have just said 'what we do now gaffer? What's the point?'
"You've got to hope the linesman can see it. VAR has got to be the answer to help them out, it would have sorted the goal out within seconds."
Chelsea's win took them to within one point of fourth-placed Manchester United and kept alive their hopes of a Champions League spot.
But manager Maurizio Sarri, who left star forward Eden Hazard on the bench until the 53rd minute, was a target for the travelling supporters during the second half.
The Chelsea fans sang 'we want Sarri out' and 'you don't know what you're doing' before the late goals.
Sarri said: "I don't want to answer, but I can understand the reaction of the fans.
"But it was probably best for them to wait until the end of the match. I am getting used to this and for me, it's not a big problem.
"I just have to work to change their opinion. If I win matches, then the fans will be happy.
"We were lucky with the first goal. But I think we deserved to win and, sometimes during a season, you need to win matches like this."