I like del Potro as well (who doesn't?) but I think this whole "tennis needs him" meme is a bit misplaced, or at least a few years past date. Delpo was supposed to be the guy that turned the Big Four into a Big Five...One could easily imagine that 2009 year-end Top 5 continuing for a half decade or more, in some form or fashion. But it wasn't to be, and instead we got Big Four dominance, until Stan came along in 2014.
So I think tennis "urgently needing" Delpo is more relevant four or five years ago. Stan broke up the party in 2014, and then Cilic book-ended it later in the year. And Stan has been there, winning a Slam each year, reminding all of us that the Big Four are beatable.
I wrote
an article over at Tennis Frontier that talked about the frequency of new Slam winners, and why there should be a new Slam winner in 2017, if the year follows historical trends. If there's not, it will be the first time in the Open Era that we've gone three full years without a new Slam winner. That said, after seeing Roger win AO, and knowing that Rafa, Andy, and Novak will be hungry to get their titles (not to mention Stan), it might be hard for a new champion to emerge. Probably in 2018.
But back to Delpo. My point is simply that tennis might have urgently needed him in 2010-13, when the Big Four won every single Slam, but now not only do we have Stan in the mix, but there's a young cohort that is stronger than five years ago. What I think tennis urgently needs is for those young players--be it the "older" (relatively speaking) Dimitrov, Raonic, and Nishikori finally breaking through, at least in the Masters, or the younger generation of Thiem, Kyrgios, Zverev, etc, taking a step forward.
That said, Delpo could be a stealth dark-horse. I've said here or at TF that I think we're going to see the Big Four hegemony start to break up more on the Masters level; the Slams will still likely be dominated by the usual suspects, but I could see a Masters or three going to a new champion. Delpo still hasn't won one, so he'd be a prime candidate. A Slam? Hard to see it at this point, but you never know.