Defense is underrated. Murray would return Safins shots that he'd have no right to return and either gain advantage in the rally and hit a winner or force Safin into error.
Basically---a Berdych-Djokovic type of match. We know who mainly wins those !
Djokovic is better than Murray and Safin is better than Berdych, so not really the same situation.
Not to mention that, as Leng Jai pointed out, that could happen in todays conditions. In a faster court Safin would blow Murray of the court.