SAN ANTONIO — Stephon Castle might be stuck between a rock and a hard place. On one hand, the San Antonio Spurs' star two-way guard can let up on his physicality, allow the Minnesota Timberwolves easier shots near the rim and allow himself to be pushed around more than he does. His other option is missing the final minutes of every game. Castle didn't actively choose the latter for himself Monday night, but such was his fate as he watched Julian Champagnie's final 3-pointer hit the front iron from the bench. San Antonio dropped Game 1 to Minnesota 104-102; Castle accrued 17 points and six fouls in 28 minutes. "It's frustrating," he admitted on Tuesday. "Other teams are playing as physical as us ... sometimes the calls just don't go our way, but I can't change who I am defensively." As the Spurs' first line of defense, Castle often faces the NBA's best slashers and scorers.…