While the Raptors try and sort out what to do with free-agent-to-be Kyle Lowry before the trade deadline on Thursday, they're trying to put together a contingency plan.
And according to the Toronto Star, that included the Celtics' Rajon Rondo.

It's no secret Boston has dangled four-time all-star Rajon Rondo league-wide and while the asking price is steep, he has piqued the interest of Toronto's front office, according to multiple sources. Toronto is eager to up its “star” quotient and is also enamoured with Rondo's resume, particularly his four all-defensive team selections (two all-NBA first team). He has many backers in the organization.

However, Rondo tore his ACL just over a year ago, has only played in 10 contests this season and will become an unrestricted free agent in the summer of 2015 after earning $12.9 million next year.
Rondo has consistently had his name pop up around this time every year, but the Raptors would have to part ways with a considerable amount of assets to make it happen. One recent report suggested the asking price is two first round picks, something the Raptors have, but with this upcoming draft so loaded, may not be willing to part with.

Again, so much of this is going to have to do with Lowry and what happens with him. He's set to be an unrestricted free agent and with him playing so well, his price is only climbing. So the Raptors are looking for a backup plan in case they decided they have to move him now.

But Boston isn't going to let go of Rondo easily. He's their most valuable trade piece and someone that still could be part of their rebuilding. The moment you trade a player like Rondo is the moment you start looking for another guy like him.

http://www.cbssports.com/nba/eye-on-basketball/24447405/rumor-raptors-have-interest-in-rajon-rondo