Florida opened the season by winning two of its three meetings with the Mets.
Robertson (1-0) struck out four and did not walk a batter, throwing 54 of his 94 pitches for strikes. Burke Badenhop worked three innings and Leo Nunez came on in the ninth to collect his first save.
The loss went to Jon Niese (0-1), who allowed three runs on eight hits with three strikeouts in six innings.
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