Tiago has been nursing a calf contusion for quite some time now, and I'm sure that Popovich is "happy" that he is available with Timmy getting a much deserved night off.
The official release:
SPURS INJURY UPDATE
Tiago Splitter (right calf contusion) will play in tonight's game at Portland. Splitter has missed the past four games with the injury.
Additionally, Tony Parker (rest), Tim Duncan (rest), Kawhi Leonard (non-displaced fracture of the fourth metacarpal; right hand) and Aron Baynes (left knee contusion-hyperextension) are all listed as out for tonight's game.