Despite an impressive first campaign at Manchester United, Owen Hargreaves admits he was only ever "60 per cent" fit last season.
Hargreaves, who is still struggling to shake off a long-term tendinitis problem, said: "There is a lot more to come from me.
"When I had another scan on the knee this summer it had not improved, so I came back early to try to fix it at the beginning of pre-season.
"Hopefully I will be fit pretty soon.
"Whether I am fit for Portsmouth on Monday, or the match after that, the most important thing is I am healthy for the rest of the season.
"I have not even come close to fulfilling my potential yet. Providing I stay healthy, this could be a really big season for me."