Phillips said: "I wouldn't say Chabal is easy to defend against, but he has a very effective game for what he does.
"It's predictable but effective and he will take route one and - as England have found out to their disappointment - if you don't deal with that initial contact, he has the ability to regenerate his momentum and once he gets behind the first line of defence he's a huge threat."
Phillips says France's skipper for the rivals' last pre-World Cup warm-up game, Serge Betsen, is also a major threat, but that Wales cannot afford to concentrate too much on getting to grips with him and Chabal.
He continued: "Chabal is going to be a key player as a ball-carrier and Betsen is very, very physical around the ruck area.
"We want to highlight certain areas, but not get too bogged down trying to mark individuals when the structure of the attack comes at us across the length of our defence."
Phillips was happy with Wales' defensive display against Argentina last weekend, but says in some ways that aspect of performance was better in the 62-5 defeat to England at Twickenham on August 4.
The former dual-code international says Wales' disciplinary problems gave England the chance to establish close-range attacking platforms at Twickenham.
He explained: "We didn't concede many line-breaks or tries against Argentina and that's a step up from the England game.
"But believe it or not, at times I thought our structure wasn't as good as it was in the England game, but overall it's certainly an area that is improving every time we play.
"I don't want to keep harking back but while we conceded a lot of tries against England they were more from defensive indiscipline than a lack of structure and they put us in positions were England were hoping to be.
"I think we addressed that against Argentina. Our discipline was something we focused on all last week and it was pretty good - in fact it was very good against Argentina and as a result we weren't in those pressure zones so often."