The 28-year old kept two clean sheets in Scotland's recent friendlies against the USA and Norway and Strachan suggests he is now ready to challenge Hull City's Allan McGregor for the number one shirt.
"I've known David for a long time and he's now got a presence about him that he didn't always have," said Strachan.
"It's not arrogance, it's just a self-confidence. He hasn't changed off the pitch. He's still a very quiet and unassuming man but there is now a presence on the pitch.
"Is he now putting Allan McGregor under pressure for the number one spot? Yeah, I think he is."
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