Oxford United left winger Craig Nelthorpe has been made well aware of his responsibilities to the team this week.
The former Doncaster Rovers man was subbed at half-time against Barrow last Saturday.
He had been yellow-carded and was close to the edge, especially with a referee who at times didn't appear to know what he was doing.
Manager Chris Wilder said: "I thought tactically we needed to do something and change it around at half-time.
"And I'll be honest with players, and I wasn't happy with Craig in how he went about things. But he's a young boy, who's learning his trade and is not always going to get it right.
"They need telling, and they'll be told in the right way. If they learn from it, then great. If they don't, then we have problems.
"We don't have prima donnas here at this football club. It isn't about individuals, it's about how we do as a group, and we've done OK as a group."
OXFORD United have offered seven of their Under 16 team a place as scholars next year.
The seven are Matthew Clark, a midfielder from Wantage, Matthew Willett, a full back from Headington, Jamie Connor, a midfielder from Reading, Aaron Woodley, a striker from Abingdon, Conor McDonagh, a midfielder/striker from Cowley, Daniel West, a midfielder or striker from Thame, and Sam Parish, a defender or midfielder from Didcot.
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