The 24-year-old has been out of action since August 2010 after suffering a second knee injury as he prepared to return to action after an initial lengthy lay-off with cruciate ligament damage. Following several practice matches, Campbell played and scored for the reserves last week, and is nearing the point where he can be considered for selection by Martin O'Neill.
The former Manchester United player told the club's official website, www.safc.com: "It's always good to get a goal, but the most important thing is making sure the knee is all right."
He added: "I have been training for a while and the big thing is that these things take time. As much as I want to be back playing, I know everyone's got to be talking to each other to make sure the knee is sound.
"I'm almost having to hold myself back. This is one of the worst parts - those final few weeks just seem to drag, but I know I have to take it steady."
Having come so near to a return in April last year, Campbell is not prepared to leave anything to chance after being forced to write off such a large proportion of the last two years of his career.
He said: "The training-ground matches have helped me, I haven't felt sluggish or anything.
"But rushing things results in niggles. When I come back I want to be at my best, I don't want to be half-hearted."