Manning compared the 6-foot-4, 230-pound Marshall's size to that of his former big target, Plaxico Burress, who helped the Giants to a Super Bowl win during the 2007 season.
"I think Plaxico was kind of the last one similar to that size," Manning told the New York Post on Thursday night before being honored at the National Football Foundation. "They can be open when they're not really open. You don't want to get into a habit, it's not a jump-ball but you can throw him open. He's been in lots of offenses and he gets open a lot of different ways, very disciplined in his route-running and understanding concepts. I think he'll be good for that receiver room and in our locker room, having that veteran presence."
The 36-year-old Manning threw to Marshall for the first time earlier this week at Duke University during a passing session attended by other Giants receivers.
"I was excited when we made that acquisition,'' Manning said of Marshall. "He's obviously a big target and smart, asks a lot of questions, he's going to pick up the offense quickly. And he's excited. He's excited about coming to this offense and staying in New York and having a No. 1 receiver (Odell Beckham Jr.) on the opposite side of him.''
Marshall agreed to a two-year deal with the Giants last month after being released by the New York Jets at his request.