He should be rated as a keeper with:
Strong positioning/pnticipation
Penalty saving skill
Relative solid reflexes (due to his "flexibility")
"World class" mental strength (probably linked with his anticipation)
Thing is that he was described as a "keeper who almost never lost concentration" (which i guess means straight up a solid MEN/GKS combo.
And since he is consistently ranked as one of the "very best" argies keepers; do your math!