Ferrer's opponent Wednesday will be unseeded Jurgen Melzer, who rallied past Albert Ramos, 2-6, 6-3, 6-3.
Nadal will meet Jurgen Melzer next, after the Austrian overcame Spain's Daniel Gimeno-Taylor 6-3 7-6 (7-2).
Meanwhile, Jurgen Melzer denied Milos Raonic a second successive title by winning the Memphis hard-court event on Sunday.
The Scot, 23, will next face Argentine Juan Monaco, who beat Jurgen Melzer of Austria 6-7 (6-8) 7-5 6-2.
Spain's Ferrer will play Austria's Juergen Melzer for a place in the semifinals.
Two seeds suffered shock defeats as Spain's Nicolas Almagro, the No. 10 seed, was knocked out by Austrian Jurgen Melzer.
The 23-year-old Scot, still yet to drop a set at the event, next plays Jurgen Melzer who beat Marcos Baghdatis.
Jurgen Melzer reached the final of the Memphis hard-court event on Saturday, beating Czech third seed Radek Stepanek 6-4 3-6 6-3.
Melzer will face last year's runner-up Milos Raonic on Sunday after the in-form Canadian defeated Germany's Benjamin Becker in straight sets.
Austrian Jurgen Melzer , the 13th seed, battled to a 6-4 6-7 (4-7) 6-3 1-6 7-5 win over Ricardas Berankis of Lithuania.
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He'll now face the No. 10 seed Nicolas Almagro or Jurgen Melzer.
Next up for Haas is third seed David Ferrer, who came from one set down to defeat Austria's Jurgen Melzer 4-6 6-3 6-0.
"We could use two of those plants tomorrow if they can bring them on line, " says Steven Melzer, a Midland, Tex. oilfield consultant.
Wawrinka, meanwhile, will next face world No. 8 Jo-Wilfried Tsonga, who defeated Austrian Jurgen Melzer 6-3 6-0 the day after the Frenchman's 28th birthday.
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Earlier in the day, Almagro needed under an hour to dispose of Austria's Jurgen Melzer 6-3 6-1, to reach his first-ever masters tournament semifinal.
He also has more match wins than any other player on the ATP Tour this year, with Wednesday's win over Melzer his 24th of 2013.
The Austrians now need Jurgen Melzer to defeat David Ferrer in the open singles rubber on Sunday if they are to keep their semifinal ambitions alive.
In more substantive criticism, Melzer said that the new study had left out more than 400 survey respondents, implying those excluded could have skewed the results.
The other semifinal will be between 2006 Australian Open finalist Marcos Baghdatis of Cyprus and 21-year-old Bulgarian Grigor Dimitrov, who upset Austrian seventh seed Jurgen Melzer.
The LaKind-Goodman study identified what appear to be two anomalies in the analysis by Melzer and two other related papers released in 2010 and 2011.
Meanwhile in Castellon, Spain took a firm hold on their tie against Austria as Nicolas Almagro and David Ferrer recorded straight set wins over Jurgen Melzer and Andreas Haider-Maurer respectively.
Former world No. 8 Melzer followed up his semifinal victory over American top seed John Isner and his earlier win over former finalist Radek Stepanek to claim his fourth ATP title.
World No. 46 Andreas Seppi beat his fellow Italian, qualifier Stephane Bohli, 6-1 7-5 to set up a second-round clash with either Serbian eighth seed Viktor Troicki or Austria's Jurgen Melzer.
Sixth seed Roddick, who lost the 2004 and 2005 finals to Federer, was pushed hard before beating Jurgen Melzer 7-6 (7-2) 7-6 (7-2) 4-6 6-3 after almost three hours on court.
Tenth seed David Ferrer was taken to three sets in a 3-6 6-3 6-4 victory over Alexandr Dolgopolov but 13th seed Jurgen Melzer had little trouble in dispatching qualifier Santiago Giraldo 6-1 6-4.
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The 31-year-olds, ranked 35 and 37 respectively, have both won tournaments this year -- the Finn winning the Apia International in Sydney in January while Melzer took the Memphis title the following month.
Almagro was on court for just under two hours in his 6-2 6-2 6-4 win over Melzer while world No.5 Ferrer demolished Haider-Maurer 6-1 6-3 6-1 to continue his unbeaten status in Davis Cup singles matches.
And Del Potro, who said that he suffered from similar wrist tendinitis earlier in the year, pulled up in his match against Melzer to ensure only two of the top six players are left in the draw.
Melzer and the primary author of the diabetes study, University of Michigan doctoral pre-candidate Monica Silver, also pointed out that the new study included children in the diabetes assessment, which could also account for the different conclusions.
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