NEW YORK — It's Enyel De Los Santos' turn to make a first impression.

The Phillies are expected to call up De Los Santos from triple-A Lehigh Valley for a spot start against the New York Mets on Tuesday night at Citi Field, manager Gabe Kapler confirmed Monday. The 22-year-old righthander will be the third Phillies pitcher to make his major-league debut this season, joining relievers Seranthony Dominguez and Austin Davis.

De Los Santos is needed because righthander Vince Velasquez (bruised right forearm) isn't eligible to be reinstated from the 10-day disabled list until Wednesday. Velasquez "almost certainly" will start the series finale Wednesday night, according to Kapler.

Acquired from the San Diego Padres in an offseason trade for shortstop Freddy Galvis, De Los Santos leads the International League with a 1.89 ERA in 16 starts. He's tied for sixth in the league with 87 strikeouts in 95 1/3 innings. He was also selected as the Phillies' lone representative in the All-Star Futures Game on Sunday in Washington.

To open a spot on the 40-man roster for De Los Santos, the Phillies are expected to place infielder Pedro Florimon on the 60-day disabled list. Florimon has missed the past five weeks with a fractured right foot.

Entering Monday's doubleheader against the Mets, the Phillies' rotation ranked fourth in the National League with a 3.80 ERA. Righthander Zach Eflin's breakout season has been a pleasant development for the rotation. And with Velasquez set to return and De Los Santos representing depth at triple-A, the Phillies figure to prioritize offense and relief pitching before the July 31 trade deadline.