Things are about to get very interesting with Chris Johnson. The second-year swingman will finish his second 10-day contract with the Celtics tomorrow at midnight, and the club will have an important decision to make.

NBA rules do not allow a player to sign more than two 10-day deals with the same team in a given season, so the Celts must either ink him to a guaranteed contract for the remainder of this season or set him free in the open waters of the NBA market — where, after his strong showing here, there are an increased number of sharks.

There is every indication the C’s would like to keep Johnson, but they also have an important need to maintain roster flexibility as the Feb. 20 NBA trade deadline approaches.

According to the league office, the Celtics could not enter into any binding agreement with Johnson now that would not begin until after the deadline.

The Celts could, however, tell him that, if a roster spot is available on Feb. 21 and they can stay out of the luxury tax, they would be interested in signing him for the rest of the year. They could also sweeten things by saying they’d be amenable to making some financial guarantee that would bring him to next season’s training camp, as well.

In that scenario, there would be nothing binding on either side. No promises would have been made. Johnson would be free to accept a call-up to another NBA team — or even sign a larger deal elsewhere — and the C’s would have no recourse. But if Johnson believes the Celtics give him the best chance for longer term employment, he could also choose to refuse offers from other clubs.

In his second season out of college, Johnson knows that it’s more important to find the right NBA situation. He also knows the Celts appreciate his skills off the bench.