McIlroy tied for 45th at last week's Houston Open, where Horschel was joint second behind D.
Horschel jumped from 60th to 24th on the money list after a second-place finish at last week's Houston Open.
He arrived at the Houston Open having failed to break 70 in his last nine rounds on the PGA Tour.
He replaced Rory McIlroy, who has a chance to get back the No. 1 ranking this week at the Houston Open.
Meanwhile on the PGA Tour, former British Open champion Louis Oosthuizen of South Africa led after three rounds of the Houston Open.
In-form Casey won on the European Tour in Abu Dhabi earlier this year and recently recorded his first US PGA Tour victory in the Houston Open.
The world's No. 2 player closed out his week at the Houston Open by making a 25-foot birdie putt for a 70 and a tie for 45th.
Points returned from the long delay by making four pars, and the last one from just outside 12 feet gave him a one-shot victory in the Houston Open.
Casey insisted he was back to full fitness after withdrawing from the defence of his Houston Open title last week after hurting his shoulder and neck in practice.
The 75th Masters tees off on Thursday at Augusta National, and defending champion Phil Mickelson rides into the tournament on a high after winning the Shell Houston Open last weekend.
Mickelson, who clinched his fourth major crown at last month's Masters, had not missed a cut on the PGA Tour since the April 2009 Houston Open, a run of 21 events.
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And one unsung character in this story is Ron Streck, the journeyman U.S. player was the first to win a PGA Tour event with a metalwood, the Houston Open in 1981.
McIlroy aims to get back in the swing -- and respond to the gauntlet thrown down by Woods at the Houston Open, where he could return to the No. 1 ranking with victory.
Houston had an open spot in the rotation after demoting Brad Peacock to the bullpen this week.
In contrast with recession-battered places like Phoenix, Houston remains remarkably open to migrants from the rest of America and abroad.
By Sunday afternoon, 151 of Valero's Houston stations were open again, but only half had gasoline, and they were quickly running out.
Hassell said 50 bank branches out of 140 in the Houston area were open Tuesday morning -- up from 33 on Monday -- with work continuing to open more.
Meanwhile, Pennington moved from Santa Clara headquarters to open a Houston office of WhiteHat.
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The school is open to all of Houston's taxpayers, but children of the medical center's employees account for virtually the entire enrollment.
Group1 Automotive, a national dealership chain based in Houston, is gearing up to open a big call center to help people who shop on their smartphones.
With the recent news about Texas Governor Rick Perry announcing that the Lone Star State is wide open for business, Houston makes for a fitting place to explore how this professional sport might have been different if earned income did not move at rocket speed.
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In addition to the Canadian expansion, the company plans to open stores in Jacksonville, Florida and Houston Texas.
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The TeamWork Online platform became the solution in 2000 when the Houston Texans joined the NFL and team management needed to promote their open jobs, but wanted to avoid a deluge of unqualified applicants.
Petrobras has elected to keep its doors open in the Islamic Republic, and it also has an office in Houston.
Caterpillar, for example, one of the likely beneficiaries of expanded exports, recently announced plans to open a new assembly plant not in its Midwestern base but in Victoria, outside Houston.
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Altuve grounded into a fielder's choice with the bases loaded in the second and Houston went down three in a row following Jason Castro's double and Pena's walk to open the third.
Jose Altuve grounded into a fielder's choice with the bases loaded in the second and Houston went down three in a row following Jason Castro's double and Pena's walk to open the third.
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