Classic 4-4-2 formations have enabled McClaren's reign to get off to a flying start with three straight wins.

But the loss of his first choice holding player, Owen Hargeaves, to a broken leg means the England coach has some thinking to do ahead of the matches against Macedonia, here on Saturday, and in Croatia next Wednesday.

"We might have to change it a little bit because losing a big player like that just changes the balance of the team," the former Middlesbrough boss admitted.

Tough-tackling duo Scott Parker and Phil Neville offer McClaren the chance to replace like with like, while Manchester United's Michael Carrick will be hoping for another opportunity to display his impressive range of passing at the base of a midfield diamond.

"I haven't decided who it will be but I have something in my mind for the two games," McClaren said. "Players have to be adaptable and flexible. They have to be intelligent and be able to adapt to different roles and different responsibilities.

"I'm not averse to changing systems. I was very flexible at club level, playing 4-4-2, 4-5-1, 4-3-3 or 3-5-2, to adapt to any situation and to adapt the players within that.

"The players have to be intelligent and I think at international level that's what you need. I firmly believe that you can't just have one system and be rigid in that."

McClaren will not however be abandoning his commitment to constructing a side with real pace throughout and the ability to turn defences through the use of skilful wide players, an objective which has contributed to the one-paced, non-dribbling David Beckhamn being left out in the cold.

"Our game is about tempo, keeping a high tempo, but international football, European football, is totally different and perhaps we have to adapt," McClaren added.

"We need to play with periods of intensity and to have periods of non-intensity, but we should always be in control of the game."

Having beaten Macedonia with something to spare in Skopje last month, England will be confident of improving on that 1-0 victory at Old Trafford on Saturday.

But the trip to Zagreb to take on a Croatia team managed by former Everton and West Ham defender Slaven Bilic has the look of a mission that, handled badly, could bring about the end of McClaren's honeymoon period.

"Croatia is a big test for any team," he acknowledged. "They are a very good team technically. I had a chat with Slaven recently and he told me they had a very good young team. In Croatia you're also dealing with the atmosphere, the intensity of the crowd, so it will be a big test for our players."

Carrick, 25, is expecting McClaren to mix things up a bit this week.

"He's talked about 3-5-2, and throughout the games that he's been in charge he's changed formations," the Manchester United midfielder said.

"We have a home game and an away game coming up, and I wouldn't have thought the manager would want to play the same way in both matches.

"I haven't really played the holding role since I went to Manchester United. I've been getting forward more than I did in all of my Tottenham career.

"I really enjoyed playing that role at Tottenham, but it's a slightly different system at United and we sort of take turns in doing the role.

"I'm getting used to being in more forward positions, but I'm comfortable playing the holding role because I've done it for so long. It comes pretty naturally."