Very emotional night for me personally, the recuperating Mullen shared via the Irish groups Twitter account.

But he is here with us!

And we are very grateful that he did and that hes here with us tonight.

Bono, The Edge, Adam Clayton and Bram van den Berg perform during opening night of U2:UV Achtung Baby Live at Sphere

Kevin Mazur/Getty

We wish him a speedy, speedy, speedy recovery.

Bono said van den Berg saved the day when Mullen had to bow out of the Vegas shows.

“His name is already legend around here to people who can pronounce it.”

The next group scheduled to perform at the Sphere isPhish, which will kick off its run in April.