Robertson admitted the defeat was a difficult one to accept.
"The dressing room is quiet, devastated," the Scotland left-back said. "That is what happens when you don't win finals.
"We had chances, came up against an unbelievable keeper. Being honest though, we could have played better.
"We are a pressing team, it has worked so much for us but we have been caught [at the] back post and that's football.
"It is hard to get back in the game playing against against a very experienced team, they know how to see out a game."
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