Justice Department antitrust chief Makan Delrahim, who is leading a review of the proposed $26.5 billion merger of Bellevue-based T-Mobile US with Sprint, says the elimination of one major competitor in wireless service isn’t necessarily a deal killer. The law and market economics will be the crucial factors, Delrahim said Friday, answering whether the U.S. would allow the number of major players in mobile phone service to shrink to three from four now. “I don’t think there’s any magical number that I’m smart enough to glean about any single market,” he told reporters following a speech at the Council on Foreign Relations in Washington. Delrahim’s comment echoes the position taken by Federal Communications Commission Chairman Ajit Pai last year and marks a reversal of the stand that regulators outlined under the Obama administration. Their insistence on a four-player market made a potential Sprint-T-Mobile merger a non-starter in 2014.