April 23 (Reuters) - Robin Van Persie's 24 goals fired Manchester United to their 20th league title but manager Alex Ferguson was quick to praise the contributions of some of his unsung heroes. Michael Carrick consistently held the midfield together with calm assurance and young defenders Rafael and Phil Jones were singled out by Ferguson as players who have made huge strides. "You saw this season an incredible improvement in the boy Rafa," Ferguson said as the celebrations kicked off at Old Trafford following Monday's 3-0 win over Aston Villa. "He has had a fantastic season. ... More...