President Trump responded to incoming Sen. Mitt Romney, who criticized the president in a blistering opinion piece, by urging the Utah Republican to be a “TEAM player & WIN!”

“Here we go with Mitt Romney, but so fast! Question will be, is he a Flake? I hope not. Would much prefer that Mitt focus on Border Security and so many other things where he can be helpful. I won big, and he didn’t. He should be happy for all Republicans. Be a TEAM player & WIN!,” Trump wrote on Wednesday.

Trump referred to retired GOP Sen. Jeff Flake, who became a constant critic of the president in his final year in office.

Romney, who will be sworn in on Thursday, wrote in the Washington Post on Tuesday that Trump “has not risen to the mantle of the office.”

Romney, the Republican presidential candidate in 2012, said he will not respond to every Trump tweet and will support policies that are in the interest of the country but “oppose those that are not.”

“I will speak out against significant statements or actions that are divisive, racist, sexist, anti-immigrant, dishonest or destructive to democratic institutions,” Romney wrote.