Mansfield midfielder Kyle Nix has been suffering with a calf problem and is unlikely to feature.
Goalkeeper Andy Marriott requires groin surgery and will be sidelined for around eight weeks, so Mihkel Aksalu has been brought in on loan for cover.
Rushden and Diamonds manager Justin Edinburgh tells BBC Radio Northampton: "That's four goals in six starts for Aaron O'Connor. He's looking sharp now and he'll only get better.
"The play-offs are our ambition. We massively overachieved to get there last year, and we're overachieving again.
"If we show the commitment and work ethic we did against Darlington, then who knows."
Source: BBC Sport