The 24-year-old has suffered from continual fitness setbacks since move from Manchester United in 2009, but appeared to be on the road to recovery January when he scored twice in his first two appearances back following an 18-month stint on the sidelines, even earning an international call-up.
But, despite a consistent run in the team, his goalscoring form did not return and Campbell is hoping the new Premier League season will hand him a clean slate.
Campbell told The Evening Chronicle: “I need to get some proper fitness under my belt. I have been miles behind the rest of the lads so it will be good to get a fresh start.
“When you don’t get a good run of five or six games in a row, it’s pretty hard to get match fitness.”
However, Campbell understands he faces competition next season as Martin O'Neill wants to make additions to his attacking options, meaning the striker must impress again during pre-season.
He said: “Last season when I was still injured, the aim was just to get fit and then get a proper season with a fresh start.
“That’s still the aim now. My last pre-season was really good and I had a good scoring run. If I can have another one like that, I will be really happy.
“I started that pre-season well and started the season well.
“If you have a good pre-season, it helps you a lot. During the season, training is not as hard and you get that good solid base of fitness.”