But the Blues boss admitted he was disappointed not to claim all three points against the Londoners.
Blues had a number of chances to take a first half lead, before Wes Thomas broke the deadlock minutes after the break. But The Lions fought their way back into the game and scored a 70th minute leveller.
"It was another game today where I think we’ve done some good things with the ball in the first half and created some good chances and then gone on to take the lead," he said.
"But in both halves we’ve given the initiative back to Millwall really and we’ve let them cause us problems. It was probably a fair outcome but I’m disappointed with it."
At times Millwall used their superior physicality and experience to put a young Blues side under pressure, as Clark acknowledged.
"We’ve got pace and we’ve got power but when it comes to playing a big team like Millwall who have got big lads and are strong we looked a little bit second best at times,” he said.
"I think you could see we were a bit young and naive and because of their power and physicality they just brushed us aside at times, so we have to look at that. But what do I do? There’s not much on the bench in terms of players that would make us stronger physically and there aren’t many players on the sidelines that aren’t in the squad that would make us stronger."
Thomas's goal was his third for the club and Clark was pleased with the loanee's contribution.
"I thought he did well," said Clark. "The keeper made an unbelievable save in the first half from his volley because he couldn’t have hit it any sweeter. And he’s done well for the goal and I’m delighted for him. I just keep saying to him keep getting in the danger zones and you’ll get your goals and he did."
One sour note from the game was the sight of Jonathan Spector being stretchered off with an ankle injury.
"He's done the same ankle and it’s another blow to us," added Clark. "It’s something we have to look at because it must be Jon’s seventh or eighth injury this season, and there are two or three other players with that scenario so it’s frustrating. The thing is that not many of them are soft tissue injuries which you can prevent. The majority of them are impact ones.
"And when Nikola has gone down he thought he was fine but when he stood up he was a bit dizzy so we had to get him off asap as well."