Gasol.. Pop has wanted him for years. Notoriously didn't want to sign with the Spurs, was it in 2014? He got more money in Chicago. Pop still wanted him and when Timmy retired, Pop wasn't really ready to embrace an era that was more perimeter oriented and he wanted 2 bigs. To be fair, Pop likes Durant's game but he chose to go to GSW.
HIs initial contract was signed in the summer of 2016, a year that many foolish and over the top contracts were handed out to roleplayers. I thought the Spurs giving him his deal for just 2 seasons was a great way for them to have handled the ridiculous prices and contracts given out in 2016... but of course, then they went and splashed up 2 seasons on top of it.
