SAN FRANCISCO — With the Giants’ rotation in flux following Hayden Birdsong’s demotion and Landen Roupp’s injury, manager Bob Melvin announced following Sunday’s 5-3 loss to the New York Mets that top pitching prospect Carson Whisenhunt will start on Monday and make his major-league debut.

With a 5-3 loss on Sunday evening, the Giants were swept by the New York Mets. They dropped to 54-52 on the season, falling three games back of the final Wild Card spot. They’ve lost seven of their first nine games in the second half, and nine of their last 11 going back to the first half.

Hayden Birdsong’s demotion combined with Justin Verlander’s inconsistency highlight the team’s need for major-league rotation depth as the July 31 trade deadline looms. It’s an issue that has been brewing since the team sent Kyle Harrison and Jordan Hicks to the Boston Red Sox in exchange for Rafael Devers.