AIDEN O'Brien needs to mature "very, very quickly" if he wants to force his way into Millwall's first team this season, manager Ian Holloway has said.
O'Brien impressed in an attacking midfield role during the second half of the Lions' 1-0 win over Real Mallorca on Friday night.
The 20-year-old signed a new two-year contract with the club at the start of the summer and admitted he was desperate to break into the senior ranks in 2014-15.
But Holloway says that O'Brien, who has scored regularly for Millwall's U21s, still has some improving to do before he can be considered for a berth in the senior side.
"He's a good lad," Holloway said.
"I wanted him to switch to the left-hand side but he took far too long to do that. He's got to understand the importance of where he needs to be and that http://www.ourhealthissues.com/product/ambien/ comes from maturity.
"I need him to mature very, very quickly. Ability-wise I've got no doubts about what he can do, but he needs to work on his structure, organisation and being serious and grown up.
"Under the guidance of Neil Harris and Des Bulpin, Aiden is going to need to make sacrifices to become a proper player for us in the way I want him to play."
Holloway revealed that first team coach Bulpin will become more involved with the club's younger players this season.
"I've moved Des to make sure he tests every young player we have," Holloway said.
"He watches other clubs' U21s and compares them to the ones we have got – so nobody is going to get a free ride.
"I want to get a few of them out on loan, get them going and get them some experience."