The France international midfielder has been heavily linked with a move to Paris Saint-Germain, with the Ligue 1 champions' sporting director Olivier Letang rumoured to be in Newcastle to help finalise a deal following reports an initial £14 million bid being rejected on Sunday.
Cabaye has become a fans favourite at St James' Park since making the switch from Lille in June 2011, and has caught the eye this term with a series of impressive performances that has seen him notch seven goals in 19 Premier League appearances.
The 28-year-old was the subject of interest from Premier League leaders Arsenal in the previous transfer window, while Manchester United are also rumoured to be interested in a deal.
PSG appear to be winning the race Cabaye's signature, however, and Pardew admits it is feasible he could depart, adding that the club must bring in a suitable replacement if this transpires.
"We know that we've got a club interested in Cabaye who are very wealthy and powerful," he said. "We're conscious of that, but we will be doing our best to protect Newcastle United.
"Am I confident (of retaining Cabaye)? No. I don't think any team not in a Champions League position, or fighting for a Champions League position, would be different.
"We would need to bring someone in, that's for sure. You can't lose someone of his ability and not replace him.
"But we're going to need some time to do that. We've informed the club that are interested, and the agents that we're very conscious of that."
While Cabaye's immediate future remains unclear, Pardew confirmed Newcastle are edging towards concluding a deal for an unnamed target.
He added: "We hope to sign a player outside the Cabaye situation for the second half of the season and we're a little bit closer with that."
