West Brom boss Tony Mowbray was left "confused" by referee Rob Styles after the official chose to book Chelsea's Michael Ballack instead of sending him off during their 2-0 defeat at Stamford Bridge.
The Blues captain appeared to slap Chris Brunt in the face during the second half.
"It is a bit confusing from my point of view because he did lift an arm and slap him in the face," said Mowbray. "It was right in front of the referee and that's what he gets paid for - to referee a football match."
He added: "If he doesn't think a slap is worthy of anything other than a yellow card, then so be it. It was right in front of me and right in front of him.
"I would never call for any player to be sent off. Ballack is a world-class player, a great player, I don't know what irritated him enough to slap my player in the face but it might have helped us if we had played against 10 men for however long was left.
"But I would never sit here and say he should have been sent off. It is the referee's job to make those decisions and he didn't think it warranted it, so we accept that and get on with it."
West Brom were up against it by the third minute when Didier Drogba scored his first league goal of the season.
They conceded a second two minutes into first-half stoppage time when Frank Lampard beat Scott Carson from close range and they were two killer blows, according to Mowbray.
"The frustrating thing was the timing of the goals," said Mowbray. "We did try and frustrate Chelsea but to concede such an elementary goal so early was a blow for us.
"Going in at half-time 1-0 down would not have been the end of the world but to concede another in the 47th minute was very disappointing."
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