Stephen Ferris fears Ulster don't have the sizes to win prizes - and won't have the strength to clear three hurdles for URC title glory.
The former Ravenhill favourite does believe there is enough quality in Dan McFarland's side to win a big one-off game.
But the prospect of winning three in a row, starting with the visit of Munster to the Kingspan Stadium on Friday night, fills him with trepidation after an inconsistent campaign.
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"I think they can pitch up and beat anyone on their day if everything clicks," stated Ferris.
"We know that the line-speed they can bring in defence can really unsettle teams. We saw at the weekend with La Rochelle against Leinster, what it can do when you get up in their faces with that huge physicality.
"The only thing with La Rochelle is, sizes win prizes - and Ulster don't have that.
"When it comes to the physicality stakes, they empty their bench and it weakens the side a little bit.
"The other sides, especially the South Africans, the benches come on the sides are getting stronger.
"You're talking fully fledged internationals who have played in World Cups, played against the British and Irish Lions.
"Ulster have a big game in them, but do they have three in a row to win the URC? I don't think that they do."
Stephen Ferris will be part of the Premier Sports team bringing live coverage of all four URC quarter-finals this weekend.
He will join Graham Little, Andrew Trimble, David Wallace, Alan Quinlan, Mark Robson and Paul Marshall for Ulster v Munster on Friday night, Premier Sports 2 from 6.30pm.
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