Malachi Fields caught all three passes thrown to him for 34 yards and a touchdown in his first NFL game, after moving up the Giants' receiver group in training camp.
The Giants lost their preseason opener 13-10 at MetLife Stadium, scoring all 10 points in the second quarter. Jaxson Dart was evaluated for a concussion and returned to throw a touchdown.
Harbaugh has refused twice to say whether Jaxson Dart plays Saturday. The last time Dart faced Brian Flores' defense, he threw for 33 yards and was sacked five times.
Zvada went undrafted after a 68% final season at Michigan. Pre-draft reports pointed to short-range accuracy, not leg strength — the exact thing the Giants say they reworked.
Baltimore blew 18 double-digit second-half leads under Harbaugh, the most under one coach since 1991. Two came in his 11 playoff losses. The Giants blew five fourth-quarter leads last season.