Nothing happens, and then Leonard proceeds in spanking him all over until Cuevas is stopped along the ropes.
Cuevas certainly has a better chance of hitting Leonard...than he did Hearns...but Ray would tattoo him for about 5 rounds before Cuevas slumps to the canvas...
It would be hard to see Cuevas hit the experienced Leonard, but he would make it interesting and it would tough for Ray.
Watching Randy Shields repeatedly rip his powder puff right lead to Pipino's head, I just don't see Cuevas managing to stay upright against Ray's. As for what happens if Jose connects, see Cuevas-Shields again, as well as SRL's second career bout against Fireball Rodriguez, and when Duran stunned him in Montreal. Shields was positive that Hearns was a harder puncher than Cuevas, and Randy accurately predicted the outcome of SRL-Hearns I in an article he wrote about their upcoming WW unification. Cuevas later landed early and well on former LW Duran, and Roberto winced through it and came back effectively in short order. At WW, SRL was a tough customer.