Scotland v England: Strachan says side were 'mentally fatigued'
Scotland manager Gordon Strachan says his side let themselves down in the 3-1 defeat by England.
The Scots, who had beaten Euro 2016 qualifying rivals Republic of Ireland at Celtic Park on Friday, failed to hit the heights at the same venue.
Andrew Robertson scored a consolation as Wayne Rooney fired a brace to add to Alex Oxlade-Chamberlain's header.
"That's as good as I've seen England play in a while; maybe we were mentally fatigued from Friday," Strachan said.
"The last year has been good to us.
"We got together 10 days ago after having improved as a unit throughout the year, and our objective was to get three points against a good Ireland side. We got that and we're pleased, but we're disappointed to end our year with this defeat.
"A couple of factors made that the case tonight, and one was a determined and intense England side. We've got to say well done to England, a team full of Champions League players.
"We're a team a little mentally and physically tired after Ireland. We could have passed the ball better and England tested us in that department, that's for sure. We took on a terrific England side, as good as I've seen them play for a while."
England proved too strong for Scotland, opening the scoring through Oxlade-Chamberlain and adding a second through Rooney.
Robertson offered the Scots hope with a superb goal late on but Rooney scored his second and England's third to seal victory.
Strachan added: "We needed 10 or 11 players to play well, but if you went into my dressing room now and asked who played well, not many would put their hands up.
"We've let ourselves down, to be honest with you. But we've not let ourselves down over the 10 days, this game we have. We're disappointed with our performance.
"But we got what we wanted, the three points in our group against the Republic of Ireland."