The phrase "class performers" refers to people or things that excel or stand out in their field or area of expertise. They are highly skilled and exceptional at what they do. Full definition
It describes how world - class performers achieve peak performance. (inc.com)
It may simply be that United feel they could do with an upgrade in that department anyway, with either Fabinho or Vidal giving them more options to rotate between truly world class performers in central midfield. (caughtoffside.com)
Its pleasure to read your thoughtful and well written comments over the years, and I can only nod and bow to what you said about De Gea, he has been our only top class performer for the last three seasons or so. (therepublikofmancunia.com)