The Boston Celtics made a trade offer to the San Antonio Spurs for Kawhi Leonard before the February trade deadline but it was rejected. The Spurs never made a counterproposal to the Celtics.
San Antonio wasn't willing to even discuss trades for Leonard in February and they remain resistant to trades so far this spring.
Since then, Jaylen Brown and Jayson Tatum have become more proven NBA players while still on rookie contracts. They appear now more likely to keep their young core together than dealing for Leonard.
The Los Angeles Lakers and Philadelphia 76ers also have interest in trading for Leonard.