The San Antonio Spurs thought they were signing power forward Marcus Morris, only to see him back out of his deal and join the New York Knicks on a one-year deal. 

According to Frank Isola of The Athletic, the Spurs were not happy. 

"They're pissed," one rival general manager told Isola. 

Morris agreed to an unofficial two-year, $20 million deal with the Spurs not long after free agency opened but reneged once the Knicks had cap space open up following a re-working of a previously agreed upon deal with sharpshooter Reggie Bullock. Morris elected for the higher average annual value by signing a one-year, $15 million deal with the Knicks. 

As Isola notes, the Spurs made moves to open up cap space originally thinking they were going to land Morris by trading forward Davis Bertans to the Washington Wizards and restructuring their deal with veteran DeMarre Carroll

San Antonio has not publicly commented on Morris' change of heart. 

In 75 games last season for the Boston Celtics, Morris averaged 13.9 points per game on 44.7 per cent shooting. The 29-year-old has spent time with the Houston Rockets, Phoenix Suns and Detroit Pistons prior to his time with the Celtics. He is set to enter his eighth NBA season.