It would be so much easier if SA had a proper backup PG.
They could simply start Manu. If OKC put Thabo on Parker, then Westbrook would have to deal with Manu and he could run SAS offense if Parker struggles to do so. The problem is that the starters depend on Parker to score and facilitate. When a team kills Parker, they kill San Antonio's offense entirely.
Green is a spot up shooter, Leonard barely creates for himself, Splitter is a P&R BIG, and Duncan, while still good on the post, is not an unstoppable force in the low-block anymore.
I know my opinion is not the most popular among Spurs fans, but I think Manu should start. Start the best players and create a bench unit decent enough to play 10-12 minutes/game in the playoffs.