The Australia international was one of Villa's standout performers during the first half of the season but has not started a game since January 13th's 1-0 loss to Southampton.
Currently in Sydney for the Socceroos' upcoming World Cup qualifier against Oman, the former AZ Alkmaar star revealed his disappointment at the sudden turn in fortunes.
"The first half of the season was really good personally. It's always a learning situation when you're in a completely different competition and type of football to what I was used to in Holland," Holman told foxsports.com.au.
"I can't say anything bad about it (then) - I was playing just about every game, except for one game. After Christmas, it's hit a bit of a rocky road.
"But I've had my ups and downs throughout my career and this is another down, and I've been around for a little bit to know you've got to keep your head down and do the right things for yourself and you'll always get your chance, be it here or somewhere else."
The 28 year-old admits he does not know why he is warming the bench and only Villa boss Paul Lambert has the answer.
"You'd have to ask the coach," added Holman.
"Personally, I don't think for me a lot. But I haven't really spoken to him a lot. He's gone for a different thing and different way. But I can't give you an answer.
"I honestly don't think I've done anything different after Christmas.
"It's frustrating... something I have to deal with. Every player wants to play. When you're training every day, training hard, it's disappointing when you're not playing."