Florian Mayer is a better opponent than Starace but not by much and Murray is in a different class. I expect Murray to see off Mayer without much difficulty and we shouldn't have to sweat to see this tip come through.
Mayer also won in straight sets yesterday but crucially both sets went quite far and he lost over eight games in the match, he has had to play harder than Murray (although the Scotsman lost a set to Xavier Malisse) and I think Murray's superior fitness will see him coast through to the Semi Final, where a tougher opponent will await him.
The odds on Murray simply recording a win are poor value although at 2/7 I would reckon there is a guaranteed win. I fancy risking a little more here to go for a bigger profit.
Take Murray at 1.73 to win in straight sets and be rewarded for your bravery. If not, then be sure to get on him in the Match Result market to guarantee at least some return.