Scherzer and Harvey rank second and third in the Majors in strikeouts, with 152 and 147, respectively.
Scherzer, 13-1 with a 3.19 ERA, took his first loss of the season on Saturday, when he allowed four runs in six innings against the Rangers, who recorded a 7-1 win in Detroit. The outing snapped a string of 10 consecutive quality starts.
"13-1," Leyland said at a news conference at Citi Field. "I don't think I need to explain more than that."
The 28-year-old was the first pitcher to begin a season 13-0 since Roger Clemens in 1986.
"It means so much, especially for it being my first All-Star Game," Scherzer said. "This is what you dream for."
Harvey, 7-2 with a 2.35 ERA, has submitted a quality start in 15 of his 19 outings. The 24-year-old didn't drop a decision until June 13, when the Cardinals beat the Mets, 2-1 in New York. He opened the regular season with wins in each of his first four outings, during which he yielded a total of three runs on 10 hits.
"It's a huge honor," Harvey said. "I appreciate it. It's obviously here in New York. The fans have been great here all year. Hopefully I can make them proud."
Harvey will be the first pitcher to start a Midsummer Classic at his home ballpark since a 41-year-old Clemens did so while with the Astros at Minute Maid Park in 2004.
Harvey will also be the third pitcher to make his first All-Star Game start at his home ballpark. The others were Carl Hubbell of the New York Giants in 1934 and Esteban Loaiza of the White Sox in 2003.
"What a tremendous year he's had," Bochy said. "It really wouldn't have mattered what city we're playing in, with the year he's had."
Leyland and Bochy also announced the starting lineups. The NL lineup features Mets third baseman David Wright in the cleanup spot.
LF Mike Trout, Angels
2B Robinson Cano, Yankees
3B Miguel Cabrera, Tigers
1B Chris Davis, Orioles
RF Jose Bautista, Blue Jays
DH David Ortiz, Red Sox
CF Adam Jones, Orioles
C Joe Mauer, Twins
SS J.J. Hardy, Orioles
P Max Scherzer, Tigers
2B Brandon Phillips, Reds
RF Carlos Beltran, Cardinals
1B Joey Votto, Reds
3B David Wright, Mets
LF Carlos Gonzalez, Rockies
C Yadier Molina, Cardinals
SS Troy Tulowitzki, Rockies
DH Michael Cuddyer, Rockies
CF Bryce Harper, Nationals
P Matt Harvey, Mets