In 1340, a Nasrid-Marinid army (The former a glorified puppet of the latter) faced a Castillian-Portuguese army in the Battle of Rio Salado. OTL, the Spaniard coalition won.
WI the Muslim league absolutely crushes the Spaniard coalition, what happens next? Could we have a twin thrust into Christendom by the Ottomans (already a rising power) and the Marinids?