The Mets optioned outfielder Kirk Nieuwenhuis to Las Vegas before Thursday's game at Milwaukee. Flores is in the lineup and starting at shortstop.
This is Flores' third stint with the Mets this season. He is hitting .225 with one homer and seven RBIs in 80 at-bats.
Tejada was beaned by a 94mph fastball Wednesday at Seattle.
Mets manager Terry Collins said before Thursday's game, "(Ruben) is good. He feels great. He said he could play. We'll give him today and get him back in there tomorrow."