New Leeds coach Dave Furner will unleash the Rhinos' marquee signings against Castleford on Sunday, including former Kangaroos and NSW prop Trent Merrin and ex-Warriors and Gold Coast centre Konrad Hurrell.

Both will feature in the Kallum Watkins testimonial match at Headingley, the first and last serious hit-out before the new Super League season kicks off a fortnight later.

The Rhinos' other major off-season recruit, Tongan stand-off Tui Lolohea, played in the Boxing Day friendly against Wakefield and Furner is keen to test the strength of his new-look squad.

"We're going to pick a pretty strong side," Furner said at the club's pre-season media day. "It's probably our last hit-out.