Chris Evert has warned Serena Williams she cannot repeat the slow starts she experienced in 2015 and hope to enjoy the same incredible results.
Williams was dominant last year, winning the Australian Open, French Open and Wimbledon to complete the 'Serena Slam' and hold all four major titles at the same time.
However, she missed out on the calendar Grand Slam at the US Open, losing to Roberta Vinci in the semi-finals at Flushing Meadows.
The American's 2015 season was partly defined by comebacks. She came from a set down in the third and fourth round at the Australian Open and came back from a set and a break down twice at the French Open against Victoria Azarenka and Timea Bacsinszky.
Williams needed three sets to see off Lucie Safarova in the Roland Garros final and produced further stirring comebacks against Heather Watson - who had served for the match - and Azarenka en route to victory at Wimbledon.
But Evert - speaking in a conference call - said: "There's so many matches in the first set she played like listless tennis, lethargic, like she was going through the motions with no energy.
"She'd get it when she got mad in the second set. She would finally pull these matches out. I would like to see her start out from the first point and play some motivational tennis, then I think she won't put herself in those dangerous positions.
"She can't have another year like she had last year. She narrowly escaped so many matches, down a set, down a set and a break. It can't happen again like that. That would be like immortal for that to happen."
Williams will start the defence of her Australian Open title next week but Evert, who won two of her 18 grand slam titles in Melbourne, believes two-time champion Azarenka could pose a big threat to the 34-year-old.
"I think she's [Azarenka] a player we should be talking about and focusing on right now," Evert added. "She certainly loves Australia. She's won it twice.
"She definitely played really well last year, but kept bumping into Serena. She challenged her more than any other player.
"She's got to be one of the two or three favourites for winning the Australian Open. I always thought she has a champion's mentality."