The reality is he was never clutch. He is the greatest choker in men's tennis. I say that as a fan since his 2001 Sampras match but it became abundantly clear after 2015. Novak beat him soundly in the Wimbledon and USO finals but it was less Roger being old and Novak being at his best and more on Roger absolutely choking on every opportunity (break points). His form leading up to Novak matches was on par with his 2009-2010 days but he was playing with a larger frame which greatly reduced his shanked shots. And speaking of 2009, his matches against Haas and del Potro at the French, his Wimbledon final against Andy and his USO loss against del Potro were showcases that even still in his physical prime he was a choking dog. Excuse me if I'm being harsh. This is all well before his 2019 Wimbledon match and infamous 40-15 on serve. I am not entirely on board with it being the biggest chokejob of the men's Open Era but it's damn high up there. Of course the excuse again was his age against Novak. But that excuse has been pummeled into the dirt considering the time span between his 2010 and 2011 USO choke fests (the last being my pick for worst choke of OE for men).
Roger Federer is the absolute quintessential front-runner. That was always his edge going back to his early years. He is a fighter and thus seldom gets obliterated but in the end he rarely, RARELY wins playing from behind or at even odds. He has one of the worst track records at even odds and best of five set matches when down 1-2 in the history of the men's game. But the popular examples on
display are of course the Slams and WTF:
4-4 in 5th set of Slam Finals (0-3 when down 1-2 and 1-3 when betting underdog)
2-5 in 5th set of Slam Semis (1-4 up 2-1)
Most matches lost with MP in hand.
It's unfortunate his 2017 Australian Open run got him back a lot of ground by winning a 5 set SF match, a 5 set Final match and that final was the first he won as a betting underdog but all that was equaled by his 2019 Wimbledon chokejob. Even more were his losses in some leading and favoured positions such as losing 2009 USO up 2-1, 2010 up 2-1, 2011 not favoured but up 2-0, up 2-1 in 2005 AO SF, 2016 WMB SF, favoured to win 2013 AO SF. He also allowed the 2017 AO SF up 2-0 to go 5, heavily favoured in 2009 WMB and 2018 AO going 5.
Some additional fun facts, 2 of his 3 Slam losses up 2-0 came at his most successful Slam (Wimbledon) and against Anderson and Tsonga. His 0-2 comebacks, of which he has a shared record of 10 with Boris Becker and Aaron Krickstein have come against the following men:
Cilic
Monfils
Benneteau
del Potro
Falla
Haas
Berdych
Nadal
Sargsian
Wessels
All of whom he was seeded higher and in some cases substantially so and heavily favoured. But perhaps it is playing during Djokovic's reign who is regarded as one of the most clutch players of all time given his statistics and losing to him that elevates his inability to make comebacks against favoured or even players and constantly losing when favoured or statistically likely to finish.