Not a good thing.
The first-round pick from Illinois, whose first career start will come against the Ravens on "Monday Night Football," recently sent a text message to friend and Ravens rookie tailback Ray Rice saying he's going to have a big game against the NFL's top-ranked defense.
Obviously, Rice, who often praises the Ravens' defense as "scary," passed the text message along to his teammates, who are not taking Mendenhall's proclamation lightly.
"He said later that he was just joking, but it's too late,'' Ravens linebacker Bart Scott said. "Thanks for the bulletin-board material, rookie."
On Saturday, Mendenhall, speaking off-camera with ESPN's "Monday Night Football" crew, said he "had nothing to do with that," but did not elaborate further.
"That was news to me [when he was told about it by Steelers PR on Friday]," Mendenhall said. "Anybody that knows me knows that's not my style."
A tailback having a big game against Baltimore, by the way, is a rarity.
The Ravens haven't allowed a 100-yard rusher in 21 straight games, the longest active streak in the league. Baltimore has given up an average of just 161.5 yards through its first two games, 72.5 fewer than the league's No. 2 unit -- which belongs to Pittsburgh (234.0). The Ravens have had a top-10 defense in each of the past five seasons.
Mendenhall, who will start in place of injured Willie Parker, has carried only 10 times for 28 yards as Parker's backup, but the rookie expects a significant workload on Monday night.
Parker, the AFC's second-leading rusher, sprained his left knee late in the Steelers' loss to the Eagles last week.
This game between Baltimore (2-0) and Pittsburgh (2-1) will determine sole possession of first place in the AFC North. The teams split their two games last season.
James Walker covers the AFC North for ESPN.com.