Andrew where do you rate Nestor and Zimonjic ? I would like to hear your comment on their style ? Ziki is pretty much a power player with good feel at the net. Does the variety on returns and volleys come from nestor in this team ? You know that none of them are also not even decent singles players ?
Only doubles specialist I recall had a decent career as a single player is Leander Paes. And his team with Lukas Dlouhy is doing good also, can be a big threat if they team up for more than a few tourneys.
I rate Daniel Nestor very highly and think that Zimonjic is very lucky to be playing with him. He carried Knowles for years and will do the same with his new partner. Only difference is that Zimonjic has a stronger serve than Knowles.
I guess you have to look at your comment to see the answer. No doubles specialist can be a top flight singles player. If they were good at singles they wouldn't be doubles specialists (we'd call them all-round players). However, if you consider those highly successful doubles players who have also been highly successful singles players you'd have a much bigger list. Robert Seguso was better known for doubles but still a talented singles player. Daniel Nestor was ranked up around 58 (at age 19 he had a win over peak Stefan Edberg in Davis Cup), Bjorkman was top 10, Mirni was top 20, Santoro has been up to the top 20 (I think), Woodbridge and Woodforde had successful singles careers, so did Peter Fleming, Mark Edmondson, Kim Warwick, Paul Haarhuis, Jacco Eltingh, Anders Jarryd, John Fitzgerald, etc, etc, etc.
Truth is, the Bryans are probably the only successful team where at least one of the pair hasn't had top 50ish success in singles.
You don't think the Bryan Brothers are great? What about Flach and Seguso?
In relation to the great doubles teams, I think they're both better than average but not on a par with the likes of Sedgman-McGregor, Woodbridge-Woodforde, Emerson-Stolle, McEnroe-Fleming, Newcombe-Roche, Smith-Lutz, McMillan-Hewitt, Haarhuis-Eltingh, to name only a few of the all-time greatest doubles teams.