'Sniffer' bagged 110 goals in 273 games in nine golden years with Leeds after joining for a then British record fee of £165,000 from Leicester City in 1969.
Clarke last night geed up 19-goal striker Beckford by insisting: "What greater incentive could there be for any player than be hailed as the man who KO'd United in the Cup?
"I know enough about this game to spot a born goalscorer a mile off - and Jermaine definitely falls into that category.
"You can pay fortunes for great defenders and midfielders but, when a natural goal-grabber comes along, they will always fetch the biggest money.
"I know people make comparisons between Jermaine and me because of our records, but I don't see it. If anything, Jermaine reminds me of Andy Cole. Andy was never afraid to fluff a chance because he always believed he'd put away the next one. Jermaine is the same, he has that self-belief.
"That goes a long way towards making him a natural goalscorer and his stock will rise sky-high if he does the business against Fergie's boys - and I can see that happening."