"Gifted? Absolutely. Passionate about what he do? I've never seen that," Lewis told Fox Sports 1 on Thursday. "I don't know what that looks like."
What Lewis forgets to mention is that Flacco was the one who carried Lewis and the Ravens to a Super Bowl title four years ago with his scintillating playoff run.
Flacco, who currently ranks 29th in the NFL in passer rating, has been criticized over the years for not being emotional, including a few times by Lewis.
Flacco and Lewis, who were teammates for five seasons (2008-12), couldn't have been more different in terms of their approach to the game. Flacco has always been stoic, and Lewis was vocal and fiery.
"I don't know how many times you'll hear somebody just really go out on a limb to defend he's the greatest teammate I've ever had," Lewis said. "I don't know how many times you'll hear that. Maybe it's because his personality just isn't that personality. He's not a rah-rah guy. He won't say much. But, in the game of football, there has to be some burning fire behind you."
This isn't the first time that Lewis has urged Flacco to be more of an effusive leader. As Lewis' career was coming to a close in the 2012 playoffs, Lewis said Flacco needed to be more vocal.
Flacco has always downplayed the need to be that way. In 2013, Flacco poked fun at Lewis' passionate pregame speeches.
"I love Ray, and I love how he always spoke from the heart, but if you listened to those speeches, a lot of them didn't even make sense," Flacco said. "He meant everything he was saying, but I didn't know what he was talking about 90 percent of the time."
On Thursday, Lewis said Flacco isolates himself on the bench after a big play or bad play. He says he believes more emotional players like Steve Smith need to coax Flacco.
"It's different personalities that can make him rally," Lewis said, "because that's the only thing that can bring him out of that."
The Ravens (5-4), who lead the AFC North, play Sunday at the Dallas Cowboys (8-1).