Teammates saw it, too, and responded by razzing the rookie.
The taunts had nothing to do with Marshall making plays. After all, they've seen plenty of that in training camp.
They were about his previous position at Auburn. The former Tigers quarterback, who led Auburn to a 20-7 record and a national championship game in two seasons, has stood out during the first week of practice. He is picking up schemes, blanketing receivers and looking like a legitimate contender to make the final roster.
''Great poise, really strong competitor, and his speed and instincts are really showing up,'' Jaguars coach Gus Bradley said. ''I really like him now. I think he's got a chance. ... The thing with him is it's not too big. He doesn't care who he's lining up against.''
Although the Jaguars have depth at cornerback - Davon House, Aaron Colvin, Demetrius McCray and Dwayne Gratz have starting experience - there is an open battle for the final spot or two. And Marshall is right in the mix, maybe even at the forefront.
''It's working out very well,'' Marshall said. ''I'm getting better each day. I'm taking advantage of reps and learning from the veterans in front of me.''
Marshall was a two-way player at Pineview High in Georgia and started his college career with the home-state Bulldogs. He was a backup cornerback as a freshman, but was dismissed from the team in February 2012 for an undisclosed violation of team rules.
He landed at Garden City Community College in Kansas, where he spent a year before transferring to Auburn. With the Tigers, Marshall topped 4,500 yards passing and 1,800 yards rushing, and helped the Tigers reach the Bowl Championship Series title game against Florida State in 2014. Marshall returned for his senior season, but the Tigers went 8-5 despite averaging 35.5 points a game.
Marshall earned an invitation to the Senior Bowl, where he started the first day at quarterback but switched to cornerback between meetings and practice.
''I thought about it,'' he said. ''It was just something that I knew was the best fit for me. That's why I chose that position. It was my decision on my own. Nobody forced me to make the decision.''
It may have been the best thing for him.
The Jaguars coached Marshall on the South squad and saw firsthand his athleticism and raw coverage skills. They considered drafting him with a late-round pick, but thought they could get him as an undrafted free agent. They made him one of their priority signings, and have been pleased with the results so far.
''He's a baller,'' Colvin said. ''You really don't have to tell him too much. He's just a football player. I don't want to tell him too much because once he starts thinking, that will start holding him back.''
Added former Auburn teammate and Jaguars running back Corey Grant: ''He's just a natural athlete. I knew it would fit him perfectly. I never had a doubt in my mind he would roll into it and do it well.''
He has. Marshall intercepted a pass from Stephen Morris last week and returned it for a would-be score. He also has considerably more pass breakups than coverage breakdowns.
He has gotten some work with the second-team defense through the first seven practices, and the Jaguars plan to play him alongside the starters at some point during camp - another chance for the rookie to wow coaches and teammates.
''Really pleased with Nick's transition,'' defensive coordinator Bob Babich said. ''Very, very athletic, very, very instinctive. Just young. When I say young, just at the position. ... Very athletic and has play-making skills. We've been very pleased with him. A great young man. He's just got to continue to get better and consistency.
''He's not as analytical as some guys, but he's really instinctive.''
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