The Spurs made a commitment to Johnson in the form of a big extension. Now it’s time to figure out what type of player he needs next to him to truly excel. The forward spots have been tough for the Spurs to figure out in recent years. After mostly abandoning two big men units, San Antonio has been trying to find the right pairings that can provide the benefits of smaller lineups while not giving up a big edge on the boards and defense. It’s been a tough balance to strike. This upcoming season might be the one in which…