Aston Villa forward Jonathan Kodjia has had surgery to repair a fractured cheekbone, manager Dean Smith has confirmed.

Kodjia collided with Marvelous Nakamba during training this week and the full extent of the injury has since been revealed.

"He just clashed heads with Marvelous Nakamba in a non-competitive part of training," Smith told a press conference before Monday's home game against West Ham.

"We thought it was OK, but they've picked up a fracture at the hospital and he's had an operation on that now and he'll be out for two or three weeks."

Villa slipped to a controversial defeat at Crystal Palace before the international break and Smith has urged video assistant referees to do more to avoid confusion over contentious decisions during matches.

Smith and Villa fans were furious when referee Kevin Friend disallowed Henri Lansbury's stoppage-time equaliser at Selhurst Park.

Friend ruled that Villa captain Jack Grealish had dived during the build-up and his decision has since appeared to have been supported by the elite refereeing body, PGMOL Ltd, who omitted the incident from a list of four VAR errors made so far during the Premier League season.

"My whole thing with (VAR) is a lot of people in the stadium didn't know what was happening," Smith said.

"Usually VAR will come up on the screen and you know there's been a check, but we didn't have that and I think that led to the confusion."

Smith said that while he supported VAR, referrals, or the lack of them, for "subjective" incidents during matches was still a concern.

"Goal-line technology was brought in years ago because we wanted to know whether the ball had crossed the line and we now know if the ball is in," Smith said.

"I think the offsides are quite easy to do as well because now you know if there was a part of the body ahead of that line that they have now.

"For me, it's the subjective ones. I understand during the game we don't want to re-referee the game.

"But sometimes referees don't get a good view of incidents. So if they are going to (consult) VAR, I expect then the VAR referees to come up with a good decision, or the right decision which is helping everybody."

After being denied a point Villa slid into the relegation zone. They have lost three and won one of their first four Premier League games since winning promotion via the play-offs in May.

"We'd be sat in 12th place rather than in the bottom three, but we're not and we can't change it," Smith added.

"All we can do is move on, accept it and take it on the chin, which we have done."