We might not have seen the last of Christian Ponder just yet. With Matt Cassel hurt and Teddy Bridgewater elevated to starting quarterback, Ponder — the 2011 first-round pick whose time with the Vikings appeared to have passed — will enter this week as Bridgewater’s backup after spending the first three weeks relegated to scout team repetitions. If he’s needed, he said he’d be ready. After all, he’s now one injury away from playing. “Yeah, it’s a crazy business,” Ponder said Monday. “You always have to be prepared.’’ Ponder said he has tried to take mental reps while watching Cassel or Bridgewater in practice. He said he has spent his time since training camp started trying to learn from offensive coordinator Norv Turner and quarterbacks coach Scott Turner.