Hunter-Reay earned the 2012 championship with four wins, but this year's campaign got off to a disappointing start with an 18th-place finish at last week's season-opener in St. Petersburg, Fla.
Dixon, meanwhile, carded his fourth second-place finish in four career races at Barber Motorsports Park.
Castroneves claimed third place while Charlie Kimball and Will Power rounded out the Top 5.
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