The Blues forward Havertz saw his initial spot-kick thump back off the base of the post before being cleared away.
However, VAR ordered it to be retaken due to encroaching by the Borussia Dortmund players.
And the German, 23, coolly chose the same technique to slide into the bottom corner and put Chelsea in front on aggregate.
But his manager Potter could not watch and instead looked down at the floor.
The Englishman, 47, told BT Sport: "After the first one I thought I'll sit down now and listen to the crowd and thankfully the noise was there.
"I didn't know a massive amount, I knew they had encroached and my assistant is better with the rules than me.
"It was him or Reece, sometimes you have to let the lads on the pitch sort it, we've got confidence in Kai.
"I was delighted when I heard the roar, even though I wasn't watching.
"I'm in awe of anyone who can take penalties, it wasn't for me."
Some fans criticised the ex-Brighton chief, accusing him of weak mentality.
One said: "Potter ain't made out for that club, the guy couldn't even watch - soft manager."
Another wrote: "Potter what a p**** he no fit watch the penalty - get this guy out of the club."
A third added: "Why didn’t Potter watch the penalty, this guy man😭😭"
And a fourth replied: "Graham Potter can’t even bare to watch the penalty - what a chump."
But others praised Potter and suggested his behaviour proves just how much he cares, especially given the mounting pressure amid the poor run of form.
One said: "Graham Potter couldn't even bring himself to watch Havertz's penalty if nothing else that shows you Chelsea results matter to him."
Another wrote: "Potter couldn’t watch the penalty! For all his faults just goes to show he does care!!"
And an excited third commented: "Potter couldn’t watch because he was that nervous, proper Chels. Give this man another five-year deal and give him a statue.
"Masterclass is happening right in our very eyes, the turtle neck has yet again done magic."