The full-back has figured in just two Premier League games since the New Year, having struggled to rediscover his form after a serious knee injury.
"Phil's had a tough old season," said O'Neill. "When you're someone like him, who was injured on his second day back in pre-season, it's hard to get back to the pinnacle.
"But his fitness is improving and with that will come confidence.
"I wouldn't blame him at all if he is looking forward to seeing the back of this season so he can focus on the next one."