Not at all. Those keepers are used to playing in Europe usually the champions league and are usually established internationals(in the case of costa), playing at the top of those leagues under intense pressure and scrutiny(for likes of Porto) is far more difficult than knocking about in front of 20,000 fans at turf moor in the championship. Mentally alone its a completely different ball game. Those keepers generally havent flopped in the past and regardless of his age Traffords first season in the prem was a flop. Big money, lots of mistakes and ultimately relegation. Not necessarily his fault but he has played a part.
Im not saying Trafford is or isnt the answer, I dont know but regardless its a huge risk. Someone mentioned this is our new transfer strategy and that does seem to be the case but it also means we are gambling on whether we will compete or not which considering where we were two years ago is a massive change in mentality for everyone at the club inc us fans.