The 2019 edition of the Laver Cup is being held in Geneva, Switzerland in September and it was expected that Federer and Wawrinka would both compete in their homeland.
But on Wednesday, Wawrinka announced on Instagram that he will not be playing, instead opting to play at the St. Petersburg Open in Russia.
Federer has already signed up Rafael Nadal but the absence of his friend Wawrinka is a blow.
Dominic Thiem, Fabio Fognini, Karen Khachanov and Daniil Medvedev are also set to play in St. Petersburg which further reduces Federer’s options for Team Europe.
Federer was asked if Wawrinka’s decision was a disappointment to him and said: “Yes. This is a disappointment for me and certainly for the Swiss public.
“But I also understand his decision. I hoped he would choose the Laver Cup.
“I told Steve Zacks (the CEO) that he would do his best to bring him over.
“My priorities have always been clear; it was Rafa, Novak and Stan.
“After, he is in shape and wants to chase away the points. I understand but it’s a shame.”
Wawrinka’s decision not to play is understood to have partly been influenced by the offer received from Zacks.
And he admitted he wanted to play at the Laver Cup but was left with little choice but to turn the competition down.
“There were discussions last year, with Roger first and then our respective managers,” he said.
“The last ones took place in Australia. They made me proposals that did not suit me.
“They then told me it was their last offer.
“From there, it was pretty clear in my mind that I would not play it. It’s a choice. I wanted to [play], Roger wanted me to play it.
“Unfortunately it did not happen. And since then I have been in St. Petersburg for the past few days, my decision is now public.”