the guy is 24 ffs, people have short memories, standout player a couple of seasons ago, last season people call him average or so but he had some great games too and was one of the few players who was up to some sort of standard, I'd find 20 worse players that season under Moyes. He's also injured often but I feel it can get better, he had a bad spell of injuries at the start this campaign but so had almost everyone, then he had this cheek fracture which is quite unfortunate.
Now "sadly" Valencia somehow managed to convince Van Gaal, while Rafa's been out, with his solid approach that he's a good option and he's decent but nothing more than that. And we know Van Gaal, he takes time to make decisions. It will take Van Gaal some time but Rafael will be back He's far better talent and he will overcome those injuries to some extent. He may also have the same issue with Van Gaal as Herrera had when he was too creative and not up to do exactly what the new gaffer wanted..
Lastly he was always a player who needed no time to get in form which is why I think we should definitely keep him.
People mention names like Clyne who is steadily going to be a decent player but never as talented as Rafael, he's obviously overrated and suddenly people frustrated with Rafael's injuries and Valencia's solid play believe this player is what we need. Another example is Coleman, who is a good player but also as Clyne he's not huge upgrade even on Valencia, he also had one great season, and two solid seasons one - last season under Moyes and now the second under Martinez, nothing more than that, people are going really overboard with these players. I understand we should demand only the best but we already have a good couple of players who should share their games in the next season. Rafael and Valencia