Velasquez is scheduled to come off the disabled list Wednesday and start the finale of a four-game series for the Phillies against the Mets at Citi Field.
The Phillies earned a milestone win Tuesday, when Enyel De Los Santos won his major league debut by allowing three runs over 6 1/3 innings in a 7-3 victory.
By virtue of the win and the Atlanta Braves' 6-2 loss to the Toronto Blue Jays, Philadelphia (51-39) took over sole possession of first place in the National League East. It is the first time the Phillies have been in first place after July 1 since 2011, when they won the last of five straight division titles.
Velasquez (5-8, 4.69 ERA) will look to keep the Phillies atop the division when he caps his quick recovery from a bruised right forearm suffered after he was hit by a second-inning comebacker off the bat of Washington Nationals outfielder Adam Eaton on June 30.
Velasquez subsequently made perhaps the play of the year when he raced over toward third base, picked up the ball with his left, non-throwing hand and fired to first to beat the speedy Eaton for the final out of the inning.
After completing the throw, Velasquez -- who allowed one run over two innings -- dropped to the ground and worried over the extent of his injury as he walked off the field with a trainer.
"I thought something was broken," Velasquez told reporters afterward.
However, X-rays only showed a bruise and the Phillies placed him on the disabled list as a precaution.
Manager Gabe Kapler said following Tuesday's game he isn't worried about activating Velasquez following the minimum 10-day stay on the shelf.
"I don't have any concerns because when he came off the field the next day, he was OK," Kapler said.
The Mets (36-53) did the same thing with deGrom (5-4, 1.79 ERA), who will start for the Mets on Wednesday. He suffered a hyperextended right elbow while batting against the Braves on May 2. New York initially feared the worst for deGrom, but tests showed he was fine and the team placed him on the disabled list out of caution on May 6, retroactive to May 3.
DeGrom also missed the minimum 10 days before returning against the Phillies on May 13, when he lasted just one scoreless inning, during which he issued three walks and threw 45 pitches
Since then, though, deGrom has been the best pitcher in baseball. He has a 1.77 ERA over his last 10 starts, during which he has allowed just 53 hits and 15 walks while striking out 86 over 71 innings.
DeGrom leads the majors in ERA and was named to his second NL All-Star team on Sunday.
But deGrom is just 2-4 in his last 10 starts for the Mets, who have won only three of those appearances. They won last Friday, though deGrom didn't factor into the decision after allowing one run over eight innings against the Tampa Bay Rays. New York's Jose Bautista snapped a tie with a walk-off grand slam in a 5-1 win.
The Mets have scored just 24 runs in deGrom's last seven games, and 12 of those runs came in one game against the Colorado Rockies at Coors Field.
"We need to win games when Jacob deGrom pitches for us to be the team we want to be," Mets manager Mickey Callaway said following last Friday's game. "Those are games you have to win, when your pitchers are out there pitching deep into games and putting up better than quality starts."
Velasquez is 1-3 with a 4.61 ERA in six career starts against the Mets. DeGrom is 6-1 with a 2.74 ERA in 12 career starts against the Phillies.