Casemiro won 18 trophies, including five Champions Leagues, in his storied stint at Real Madrid. However, the Brazil international has called his current campaign with 16th-place Manchester United, who are also in the Europa League final, “one of the most successful seasons” of his career. The 33-year-old looked set for a January exit from Old Trafford after failing to impress manager Ruben Amorim, who took over at the club in…