Daniel Nardiello's two late goals in Exeter's 2-0 win provided the perfect send-off for team-mate Marcus Stewart, who announced this would be the last of nearly 800 first-team appearances in a 19-year career.
Campbell missed the game through a calf injury, top scorer Will Hoskins was also ruled out by an ankle problem, while defender Byron Anthony pulled out after feeling ill during the warm-up.
But Campbell said: "I certainly wouldn't use those factors as an excuse. For whatever reason we couldn't get going and didn't reach the standards we've set in recent games.
"To be honest we looked a bit leggy at the end of a tough period and I'm glad we now have a free midweek to prepare for our next game at Southampton.
"I've told the lads to put this setback behind them quickly and reminded them of how well they had been doing in recent weeks. We still have a big job ahead to stay in League One, but I remain confident that we can do so."
Source: PA
Source: PA