Wayne Rooney admits his first few years at Manchester United left him frustrated.
The United striker is now chasing his fourth consecutive league winners' medal.
"The club have won three European Cups and winning five is achievable, because we are the biggest club in the world," said Rooney.
"For my first couple of years at United, Chelsea looked so strong, impossible to beat really, and I was thinking 'But I came here to win things ... I'm not winning anything'. We knew we had to buck ourselves up - the players - to challenge them."