David Moyes believes Manolo Gabbiadini's opening goal in Southampton's 4-0 win over Sunderland should have been disallowed for handball.
The Italy international found the net via his upper arm to break the deadlock at the Stadium of Light, sending the Saints on their way to a first win in four games.
The defeat follows Sunderland's best performance of the season - a 4-0 win at Crystal Palace - leaving Moyes to admit inconsistency continues to plague his side.
But the Sunderland boss felt the hosts were on top before the goal, adding he believed whoever opened the scoring was likely to go on and win the match.
"That maybe sums us up a little bit, one week we can be so good and another week we can be so bad," Moyes said. "I thought we started the game really well, I thought we started very well in the first 20 to 25 minutes.
"We probably didn't create enough opportunities to score but I think we were playing well, playing with confidence, but unfortunately they scored a goal that was handball.
"Sometimes things change a game, it wasn't an easy decision for the referee to see but it was definitely taken in by his arm which makes a big difference in the game.
"I think the first goal would have been important for Southampton as well. If we had got it then they've lost quite a few games recently so it would have been a problem for them.
"It was going to be vital to whoever got the first goal. It was disappointing the referee didn't see it but nevertheless we have to hold our hands up and make sure we do things a lot better."
Moyes introduced Steven Pienaar at half-time and Fabio Borini early in the second half but the changes had little effect as Southampton scored two goals in the final minutes to add further gloss to the scoreline.
"The more attacking players we put on, the worse we became - that was just a fact of it," Moyes continued.
"Anyway, we tried and we had to do something to get back in the game.
"I didn't think we deserved to be two goals down at half-time, that was a big thing. The first goal went against us which unfortunately made it difficult."
Sunderland must wait two weeks before they are next in action against Everton, with Moyes adding: "Like everybody else we don't have a game next week so we'll be in the same situation.
"We know we have a lot of tough games to come and today was a tough game."