With just 10 minutes remaining at Stamford Bridge on Wednesday, Chelsea were on course to open their title defence with a victory after two goals from Brazil midfielder Oscar gave them a 2-1 lead over the Italian champions.
But Mikel carelessly surrendered possession with a wayward pass and Chelsea’s defenders failed to respond as Claudio Marchisio played Fabio Quagliarella into space for the equaliser.
“If I want to make up an excuse, I can,” Mikel said. “But, for me, I gave the ball away. I put my hands up, we move on.
“I’m sorry about the mistake, but there are no excuses.”
It could have been even worse for Chelsea as Quagliarella hit the crossbar with a looping shot just after his equaliser.
Blues boss Roberto Di Matteo was frustrated with the way his team lost control after taking a two-goal lead, but he could at least take heart from Oscar’s virtuoso display on his first start for his new club.
Oscar arrived from Internacional for £25 million in the close-season and he underlined his vast potential with a sublime second goal on Wednesday that saw him turn away from two Juventus markers with a sublime flick before unleashing a curling shot that flashed past Gianluigi Buffon.
It was an early contender for goal of the season and Oscar, 21, admitted he was delighted to have made such a big impact in his first Champions League appearance.
“I was very happy to score my first goal in the Champions League and my first goal at Chelsea,” he said.
“The first one, the ball deflected, so I was a bit lucky. But I was playing very well, so I could score this beautiful goal and I’m very happy with this debut.”