Why wouldn't Tsogna be able to beat Novak in that match? He's a superior grass player to Delpo. So is Berdych, he would would probably choke. I wanted to say that Delpo was 'lucky' that he was given to play Novak in those particular matches. Had he played him on 2 different occasions, I wouldn't be surprised if the H2H since 2011 was 7-1 (7-0 until few weeks ago).
And why are we even focusing on Novak? Against the top4 they basically have the same credentials. Berdych is the best vs Fed and Murray. Tsonga is the only one who beat them all in Slams. Delpo overall looks as the biggest threat to them and only one who has beaten them all more than once. Atm he is the slightly bigger threat to the top4, but not over the course of their careers.
But he is the best player between them, his Slam alone validates that. Also the career high ranking and his H2H against them...
See Wimbledon semi 2011. Even on grass, Tsonga is very prone to overhitting against the best players. Not saying he didn't have a chance, but I wouldn't put much faith on it. Especially not if he came off a 19-17 third set defeat two days before. Not sure about 'luck', I mean for instance if he had been given the chance to play Novak in WTF 2011 like Berdych I do believe he'd have beaten him there surely... but that's besides the point, in this case the numbers happen to validate my observations, but I'd have this opinion even if they didn't. Those two are fitter/healthier than JMDP and their performances vs the top guys don't fluctuate as much, but JMDP is a bigger threat. The top 4 know and are on record saying as much that, unlike Tsonga or Berdych, when he peaks JMDP is not only a 'threat' to them but every bit as good as them and can match them from the baseline without taking extraordinary risks.
We're focusing on Novak because Saberq claimed that Tsonga and Berdych made him just as 'nervous' (or not nervous) as JMDP. I disagree that he's not a bigger threat over the course of their careers though: before his surgery, not only was he a threat, he was actually one of the four best players in the world. The only period where those two were a bigger threat to the elite than JMDP was from mid-2011 to mid-2012 imo. The point I'm making here is that JMDP is more than a 'threat' to them, given a decent run of health he can match them and go toe to toe with them on a tennis court - he doesn't beat them by redlining his game on a random day and blowing them off the court, but by outplaying and outmanouevering them. Berdych and Tsonga are the defintion of 'threats': with the exception of Berdych vs Federer (a matchup Berdych can win with his normal patterns), they are guys who can catch fire on any given day and take out anyone, but who can't really hit through the top guys with their usual point construction, at least not on slow courts. Del Potro is nothing like that: he's 5-5 in the past 10 matches vs the top 4, he was 5-4 vs Fedal in 2009 - when he manages a period of semi-decent health (and therefore form) he can go toe to toe with them playing his normal game: not catching fire and taking one of them out, but matching them blow for blow.