WIGAN coach Stuart Raper has issued a warning to his team of Challenge Cup favourites.

Raper believes the leading Northern Ford Premiership outfit are a match for many of the Super League teams, a point illustrated by Leigh's fourth-round win over Salford last season.

The Centurions, who along with St Helens are the proud holders of the only unbeaten records this season, became only the fifth team of part-timers to pull off a cup shock in 78 clashes with Super League teams since 1996 with their 16-12 victory over the Reds.

"I always keep an eye on the Northern Ford," said Raper. "The top sides aren't that far off."

Sunday's all-ticket tie at Hilton Park has ignited massive interest in one of the oldest derbies in the game, although this is their first meeting in the cup for 32 years.

Leigh's last semi-final appearance was in 1987 when they lost 14-8 to St Helens and they and Doncaster, who

visit Castleford on Sunday, are aiming to become only the second non-Super League club behind Widnes to reach the last four.

Raper is full of admiration for Leigh. "They've been there or thereabouts in the Northern Ford for the last two years and they were probably very unlucky not to get promoted," said Raper.

"They beat Salford last year in the Challenge Cup at home so that's something we're aware of. It's something that will make sure our preparation is second to none."

Wigan will be at full strength with international front row pair Terry O'Connor and Craig Smith both recovering from injury.