Del Potro, who lost to world No. 3 Roger Federer in the Rotterdam final last weekend, will face 2010 champion Michael Llodra in Sunday's final.
In four of his six years in Formula One, he has watched the final race determine the champion.
He replaces Youssef Zouaoui, who was sacked after the club failed to reach the final of the African Champion's League.
And the 22-year-old's semi-final against the defending champion was also kept away from the 5, 000-capacity Centre Court, with only around 1, 200 people able to watch on Court Two.
Sebastian Vettel will start third on the grid after young Lotus driver Romain Grosjean, 26, snatched second place from the reigning world champion in the final seconds of the day's racing.
With top-ranked Azarenka and Serena Williams on the other half of the draw, Radwanska's main obstacles to reaching the final are 2011 French Open champion Li Na, who beat Olga Goortsova of Belarus 6-2, 7-5 to reach the third round, and potential semifinal rivals Sharapova or No. 5 Angelique Kerber, who advanced with a 6-3, 6-1 win over Lucie Hradecka.
There was a case to be made for Djokovic going into the final, not least because he had defeated five-time champion Roger Federer in a dramatic semi-final and had a 7-3 record against Nadal on hard courts, but the world number one is a different animal in major finals.
The Finnish four-time world champion, in his final rally before retiring, was 2mins 15.2secs adrift of Loeb.
Ferrer breezed through the final two sets after the 2001 champion Hewitt leveled at a set all.
Well, we won't know who the NCAA champion is until the Final Four is over on April 8.
He will start his 53rd grand slam tournament against 46th-ranked Frenchman Benoit Paire, and as second seed he cannot meet two-time defending champion Djokovic until the final.
PGA.com will also feature two marquee groups during the final two rounds. 2002 PGA Champion Rich Beem will provide commentary and analysis throughout the weekend during PGA.com's live coverage.
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Fellow seasoned campaigner Karen Pickering failed to make the 200m freestyle final, and world 200m backstroke champion Katy Sexton withdrew from the 50m event after coming fourth in the 100m.
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Victory over Kelly would bring Casey a quarter-final against Retief Goosen or US Open champion Angel Cabrera.
Roger Federer, who lost to Murray in the Rogers Cup final in Canada, is the defending champion in Cincinnati.
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In the girls' quarter-finals, 2008 champion Laura Robson reached the final four with a 7-5 6-1 win over fellow Briton Tara Moore.
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The Russian top seed, still seeking her first Grand Slam title after falling to Kuznetsova in the Paris final, will next play 2006 Wimbledon champion Amelie Mauresmo.
If Nittany Lions junior David Taylor defends his individual title at 165 pounds, he would likely have to beat Cornell three-time champion Kyle Dake in the final.
Retired British champion Frankel, who won 14 races on the trot, chose Royal Ascot's Champion Stakes to make his final appearance, drawing a sellout crowd of 32, 000.
He went on to set the pace in the final and beat two-time world champion Dominic Monypenny from Australia by a second and a half to claim gold.
Meanwhile, in the men's section, local favorite Marat Safin opened his final Kremlin Cup campaign by ousting defending champion and Shanghai Masters winner Nikolay Davydenko in the first round.
Meanwhile, defending men's champion Andy Murray reached the final of the ATP event in Brisbane as semifinal opponent Kei Nishikori of Japan pulled out injured in the second set.
The three finalists will then dance as usual and the audience will again vote, with the points from that added to those from the semi-final to determine this year's champion.
Klaasen, a 100-1 shot at the start of the tournament, had already beaten top seed Mervyn King on his way to the final and becomes the youngest ever world champion.
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Tilden won his six straight U.S. Open titles from 1920-1925, a record since the tournament abolished the challenge system -- where the champion automatically qualified for the final -- in 1911.
In double world champion Fernando Alonso's final appearance for Renault before he leaves for Ferrari, the Spaniard suffered the worst qualifying session of his underwhelming season to finish down in 16th.
Tilden won his six straight U.S. Open titles from 1920-1925 - a record since the tournament abolished the challenge system - where the champion automatically qualified for the final - in 1911.
Dotson made his first five 3-pointers to propel Oregon (28-8) into the second weekend for the first time since 2007, when it lost to eventual repeat champion Florida in the regional final.
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