Not so fast though! The majority assumed without deciding that the Rule 68 offer did in fact moot the lead plaintiff's claim. The liberal bloc dissented with Justice Kagan calling the majority's assumption "bogus" and resulting in the majority opinion having "no real-world meaning or application" (ouch). Justice Kagan argues that the offer in this case was never accepted and therefore the plaintiff's case was never mooted (i.e. the plaintiff was never effectively picked off).
So, if you ever have a pick-off case, be prepared to argue over whether a Rule 68 offer of judgment for full relief does in fact moot the individual's claim.