Millar admitted he desperately needs to boost his midfield options, but was aghast at the mistakes made by his defence as the borderers ran rampant.
Marc McCusker was once again on the scoresheet to take his season's tally to six in just five games but it was to prove the only bright spot.
Millar said: "If the draw with Stranraer wasn't a wake up call, then that certainly was.
"I actually praised the boys at half time as, although we were one down, I thought we had played okay, but they were a bit down and maybe didn't share my self-belief.
"Bryan Dingwall missed a good chance at 1-0 but we did equalise and from there I could only see the game going one way.
"Sadly that wasn't the case and we made mistakes that I did't think we were capable off, although that's not to take anything away from Berwick, you can't say they were lucky.
"I don't want to say we were bullied but we were certainly outmuscled in midfield and possibly even by their forwards as well. We have a couple of midfielders training with the squad at the moment and it could be we need to accelerate matters.
"But to be quite honest another one or two players wouldn't have made any difference."
Clyde travelled to East End Park on Tuesday to face first division Dunfermline in the second round of the Co-operative Insurance Cup. The Bully Wee were unlucky to lose out 3-2, having twice been in front with goals from Adam Strachan and Marc McCusker.
It's back to league action on Saturday (August 28) when they welcome Albion Rovers to Broadwood.