STEVE McClaren was quick to praise the impressive performance of one of his young stars, but admitted another could be facing a lengthy spell on the sidelines.

Adam Johnson - labelled a little diamond by his boss - was a constant danger to Charlton despite Boro going down 2-1, but McClaren revealed Tony McMahon has suffered medial knee ligament damage in a clash with Addicks' midfielder Bryan Hughes.

Eighteen-year-old Johnson, the subject of a seven-figure bid from Spurs earlier this season, tormented England full-back Luke Young and a late curling 25-yard effort brought a fingertip save from Thomas Myhre in the Charlton goal.

"We used some of our younger players like (Andrew) Taylor and (Adam) Johnson," said McClaren, who made a staggering nine changes from the side that beat Roma in the UEFA Cup last Thursday.

"Johnson will have a bright future. We know we have a little diamond there. He does the right things and he is a great character.

"You saw glimpses of the future. We have had 11 or 12 Academy players playing in the first-team and we believe in that.

"It's something we wanted to do. All our young players are English and living within a 20-mile radius of Middlesbrough.

"We have great potential if this group of players continue to progress. You can't get success straight away but we are looking to the future."

The news on Johnson's fellow teenager, McMahon, wasn't so promising. The Bishop Auckland youngster has missed five months of this campaign after dislocating his shoulder and yesterday a damaged knee ligament forced him off in the opening 15 minutes.

McClaren is hoping to find out the full extent of the injury before his squad head to the Italian capital for Wednesday's UEFA Cup second leg against Roma.

With that game topping his list of immediate priorities he felt justified in resting players at the Valley, and thought the performance, if not the result, vindicated that decision.

"All the players on duty today have represented their country at one level or another," said McClaren. "(Tony) McMahon, Johnson and Taylor have all performed for England.

"Stewart Downing emerged last season and we hope there are more to follow.

"I looked at the team and believed it was good enough and we dominated the game. I have a disappointed dressing room.

"I have to look at the greater picture. We have games coming up. We have a big game against Roma this week and another big game when we come back here for the FA Cup tie. Hopefully we'll be in better shape because of it.

"We have had injuries this year and I have not been able to make the changes I would have liked.

"Today was a great opportunity to use the squad."