The Belgian champions face Liverpool, who finished fourth in the Premier League last season, on Wednesday.
"I'm sure a lot of Belgians feel it is unfair the champions of a country have to play a qualifying round to get into the Champions League," said Onyewu.
It was worse because Liverpool were "such a strong opponent", he said.
Liege won their first title in 25 years with last season but did not get an automatic place in the group stages because of governing body Uefa's coefficient ranking list.
"I'm sure people in Belgium were hoping that once you win your championship that you would automatically qualify for the Champions League like some other countries do, such as England, Germany, Spain and so on," the Liege centre-back.
"It is going to be a very difficult two matches to qualify for the next stage of the Champions League.
"People here in Belgium were probably hoping for a more favourable draw but we are still relishing the opportunity to play against Liverpool.
"We definitely respect Liverpool. They are a great and huge club. They have a great history, especially in terms of the Champions League so we will have our work cut out for us.
"Hopefully, we will be able to rise to the occasion in the two matches that lay ahead there is always belief.
"I'm sure that the people of Liverpool are probably happy with the draw and hopefully we can use that to our advantage.
"You never know in football. We have a lot of good players here.
"Obviously, the Belgian league is not as respected as the Premier League but I feel that we have quality players that can possibly make a difference on any given day."
Onyewu spent three months on loan at Newcastle from January 2007 and helped the Magpies to a 2-1 win over the Reds in his first home game for the Tyneside outfit.
And, although he has tasted victory over Liverpool, he has played down any significance of that game heading into Wednesday's game.
"Any win against Liverpool is going to be a big win but for me it was so because it was my first start at home and first win with them," said the United States international.
"It will always stay a big souvenir for me in terms of my Newcastle experience. But that is in the past and I tend not to dwell on the past too much and try to concentrate on the future.
"A lot has changed at Liverpool. A lot of different players have come into that team."
One player who Onyewu has faced more recently is Liverpool striker Fernando Torres and he is wary of the threat the Spaniard poses.
"Fernando Torres is a great player and I had the opportunity to play against him this summer when the US played against Spain," said Onyewu.
"It was 1-0 to Spain. Torres played the first half and at the end of that it was 0-0.
"Personally, I think I defended pretty well against him, although he was also coming off an injury so he probably wasn't at 100%.
"He has a lot of different tricks in his arsenal and you have to be on your toes at all times and concentrate.
"But there is not just one player that we have to be aware of, it is the whole squad."
Onyewu was not signed permanently by the Magpies but believes he has improved since his spell in the top flight and wants another crack at the Premier League.
"I've always said that my ambitions are to leave Belgium for a bigger league. If that be England then that would be great," he said.
"I've matured a lot and progressed in a lot of different factors and aspects of my game since 2007.
"I feel as though I had a short stint in order to adapt to the style of the Premier League.
"Sometimes it takes players six to eight months to get used to the Premier League style.
"I feel as though I didn't have adequate time to really showcase what I am capable of doing. Perhaps, next time around I'll get that opportunity."
http://news.bbc.co.uk/sport1/hi/football/europe/7557148.stm
I can see where he is coming from, Champions having to play non-Champions to qualify for the Champions League. But that is how it is, the Belgians can blame noone but the Belgians for having to prequalify. Anderlecht have been pretty much regular in the Champions League and their record reads :-
00/01 L16
02/03 n/a
03/04 Group Stages
04/05 Group Stages
05/06 Group Stages
06/07 Group Stages
07/08 n/a
*n/a from my recollection means they didn't get to the last 32 .I did the analysis a while back, because of the changes to the format I have been using L16, L32 etc rather than group stages. If they played in the CL in the n/a seasons then they didn't get into the groups
Not that impressive a record, FC Brugges made the group stages three times in the last six seasons, the Belgians have two QFs between them in the entire Champions League and both came in the first couple of seasons (92/93 and 93/94) They were unlucky in the draw, had they had an easy draw then they wouldn't be whinging about it already
off, he says....
