From the ATP Rulebook regarding withdrawal from ATP 500 events:
9.03 South African Airways ATP Rankings (Singles)
C. ATP World Tour 500 – Ranking Penalty.
A player’s (Commitment and Non-Commitment players) withdrawal from an ATP World Tour 500 event whether on time or after the 12 noon deadline, shall result in a zero (0) point ranking penalty. Further non-consecutive withdrawals shall result in a zero (0) point allocation replacing the next best positive result for each additional withdrawal.
Players with multiple consecutive withdrawals who are out of competition for 30 days or longer due to injury will not be subject to a ranking penalty as long as verified and approved medical forms are provided; or, a player shall not have the ranking penalty imposed if he completes the Promotional Activities requirement as specified under “Repeal of Withdrawal Fines and/or Penalties” or if the on-site withdrawal procedures apply. Players may also appeal withdrawal penalties to a Tribunal who will determine whether the penalties are affirmed or set aside.
A player who has received a zero (0) point ranking penalty for withdrawing from an ATP World Tour 500 event may replace the zero (0) point by playing an additional ATP World Tour 500 event in that same calendar year for a total of four (4) played. The replacement tournament must be after the 500 withdrawal that has resulted in a ranking penalty. Only one (1) additional ATP World Tour 500 event
per year may be used to replace an ATP World Tour 500 ranking penalty
Seems to me as if Murray should get a 0 pointer for Basel, unless he was on-hand for Promotional Activities
, which as far as I know, he wasn't. Since there are no more 500's after Basel, then the zero pointer cannot be replaced.