The Royals released Davies on Wednesday.
Davies signed a minor-league contract with the Royals on Monday.
Davies was released by the Nationals on Friday, Mark Zuckerman of MASNSports.com reports.
Davies allowed two runs on seven hits and a walk over five innings in Thursday's Grapefruit League game against the Astros. He struck out five.
Davies signed a minor-league contract with the Nationals on Saturday that includes an invitation to major-league spring training, Jon Heyman of the New York Post reports.
Davies was designated for assignment Wednesday, Nick Piecoro of The Arizona Republic reports.
Davies' scheduled start Saturday against the Yankees has been postponed due to rain.
The Diamondbacks reinstated Davies (back) from the 15-day injured list Saturday.
Davies (back) is scheduled to return to the Diamondbacks' rotation Saturday at home against the Reds, Theo Mackie of The Arizona Republic reports.
Davies (back) allowed three runs on seven hits and three walks while striking out two over six innings for Triple-A Reno on Sunday.