Woah he didn't say he looked like Michael J Fox, he said he looked like Marty McFly. Now when I picture Marty McFly, I picture a guy who looked like David Goffin in a puffy jacket vest. Nothing inaccurate about this comparison. Nishikori in 2.
Their last meeting on hard court in Miami was 6-1 6-2, and Goffin held serve only twice in that match.
Goffin might feel 'comfy' on clay but again so does Nishikori. After Kei ripping through opposition in Barcelona, I can't see Goffin pull this one off. Two straight forward sets, unless Kei is really rusty on Madrid surface and needs time to find his game in which case a third is required (though highly unlikely)
The only way for David to beat Nishikori is to pound on him right off the bat and win it in straights. For that you'd have to assume that Nishikori is rusty as hell on the fast-ish clay of Madrid or/and feeling pain in the hip joint again. He did admit after the Barcelona final that that old injury had started bothering him again, saying "I'll have a week off until Madrid, so it should be okay." "It should be okay" from him has traditionally been a bad sign (e.g. after Miami QF 2014, Washington 2014, after Madrid SF 2014), but we'll see.
If it goes to the final set, David will have no chance against the literally GOAT final set warrior, I reckon.