IAN Holloway says he has subbed Ed Upson in Millwall's last two matches partly because he is wary of the midfielder picking up his tenth booking of the season.
Upson, along with midfield partner Shaun Williams, are both sitting on nine yellow cards for the campaign, meaning they are one caution away from triggering a suspension.
The January signing from Yeovil Town has yet to play a full 90 minutes for his new club.
"I'm very conscious of them getting banned," Holloway said. "If they get booked in the same game it will be an absolute nightmare for us."
But Holloway admits that he is eager to see improvements in Upson's performances.
He added: "Williams has slotted straight in but I think Ed's misunderstood one or two things that I want.
"I've spoken to Ed this week and he's looking more like himself in training.
"He's an attack-minded player but he hasn't quite got forward when I have needed him to. He needs to push up a bit more.
"He's a very nice lad but a very shy lad and he's got to step to the plate with us. There was a clear difference in him on Monday and Tuesday because I've now showed him what I want.
"He has not been here long enough to see some of the things I have shown the others – he didn't come to Portugal.
"It takes everybody time to bed in and I'm still learning about the club myself. But I am absolutely delighted to have the two of them for our long-term future."
Lions boss Holloway believes his midfield is missing the experience of Nicky Bailey, who is currently sidelined by a back injury.
"We have not looked the same without Nicky because he organises, talks to other players, he's brave and always wants the ball," Holloway said.
"He would have helped the new lads settle in a bit quicker and I'd have had a good talker. You can't expect a quiet lad from Yeovil to come in and organise the midfield."