Slaven Bilic felt "small West Brom" were hard done by at Old Trafford as they suffered a controversial 1-0 defeat to Manchester United.
Albion remain in the relegation zone without a Premier League win from nine matches after Bruno Fernandes' retaken penalty gave the Red Devils a first top-flight home victory of the season.
It could have been a different story if David Coote had not overturned his decision to award the Baggies a penalty just after half-time for a foul by Fernandes on Conor Gallagher.
Fernandes appeared to make contact with Gallagher's shin, but referee Coote changed his mind after checking the pitchside monitor.
To add insult to injury, Fernandes scored from the penalty spot at the second attempt soon after, with the brilliant Sam Johnstone superbly saving the midfielder's first spot-kick, only to be punished for coming off his line too soon.
Bilic could not understand why Albion did not have the chance to open the scoring from 12 yards and said his side should have had a free-kick for a foul on Gallagher just before United were awarded a penalty for handball against Darnell Furlong.
"I'm very disappointed with the decision [to overturn the penalty]. It felt like 'small West Brom'. All those crucial decisions went against us. I've watched it a few times and it's a clear penalty. I don't understand why he overturned it." he told BT Sport.
Bilic added on United's penalty: "It's a handball. It's a bit unlucky but it's handball with the rules now. Before that it was a clear foul on Conor Gallagher.
"Instead of 1-0 for us, it's 1-0 for them. When you play against Manchester United away it's a huge difference."