Roger Federer has refused to launch an all-out assault on the shaky second serve he believes Andy Murray "covers very well" in Friday's Wimbledon semi-final.
Federer was urged to "take advantage" of Murray's second-serve shortcomings by three-time Wimbledon finalist Andy Roddick, to keep his bid for a record eighth SW19 title alive.
Swiss second seed Federer eased past Gilles Simon in straight sets to book his 10th Wimbledon semi-final and a meeting with Murray, who coasted past Vasek Pospisil.
World number two Federer insisted Murray's second serve "can't be that bad", ahead of Friday's clash, a re-run of Wimbledon's 2012 final.
"We'll see," said Federer, when asked if he would attack Murray's second serve. "He's beaten me before with that second serve; it can't be that bad.
"He's beaten so many guys so many times. You know what I mean? It's something he covers very well: he's fast on his feet, he reads it well.
"He's one of the greatest return players we have in the game, and he's got a great first serve. He came through convincingly again, so he must be playing well.
"Plus he won Queen's; he's in full flight right now."
Roddick, in his role as TV pundit, said that Murray can ill afford to repeat the 64 per cent first-serve level produced against Pospisil when facing Federer.
Murray won just 56 per cent of second-serve points against his Canadian quarter-final opponent, but still prevailed 6-4 7-5 6-4.
The 28-year-old is unlikely to cope with such low statistics against Federer, who dispatched world number 13 Simon with ruthless efficiency, 6-3 7-5 6-2.
Federer set a record 116 consecutive service holds en route to his classy victory over 12th seed Simon, eclipsing the 111 mark set by Australia's Wayne Arthurs in 1999.
"It's nit-picking for sure, but the court position that's allowed (for an opponent) when he's able to stick a return is something that Murray's going to have to worry about against Roger Federer," said Roddick.
"He's someone who can take advantage of it: he's not scared to run around and can commit to hitting that forehand early."
Federer lost a five-set thriller to Novak Djokovic in last year's Wimbledon final, that record eighth title just out of reach.
The 33-year-old pipped Murray to the 2012 Wimbledon title, before the Dunblane native gained some revenge by beating Federer to the Olympic title later that summer.
Murray has restored top form after back surgery, but ran out of steam in his last meeting with Federer, at December's ATP World Tour Finals at London's O2 Arena.
Federer prevailed 6-0 6-1 but expects Murray to be in vastly different shape this time around.
"In the World Tour Finals, he came in tired," said Federer.
"He had won three tournaments back-to-back; he left everything out there making the World Tour Finals. It was not the Andy that usually shows up."
Federer admitted he was pleased to claim that stunning lengthy service-hold record, but also conceded he was "relieved" the hot streak came to an end against Simon.
"I've heard of it but then again I don't keep count when I'm out there," said Federer of moving past Arthurs' record. "I'm also relieved that I did get a break.
"I guess we're not going to talk about that anymore."