It was all going so well.

Just over a week ago, Nick Kyrgios was fresh off his first singles title and a strong showing in Dubai, while Bernard Tomic had reached the maiden ATP 500 final of his career.

Tennis was set to return to Aussie soil as a Davis Cup tie against our old foes, the US – Lleyton Hewitt’s first as captain – loomed large.

But it all blew up on Sunday as Tomic publicly questioned Kyrgios’ integrity – not once, but twice – and the latter went on a Twitter rant, telling a tennis writer to “sit the fk down”.

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Tomic, clearly hampered by a wrist problem in a four-set defeat to American John Isner that handed the US a 3-1 victory on Sunday, first aired his grievances about Kyrgios’ absence – officially through a virus – on court to Hewitt.

“While I’m here, Nick’s sitting down in Canberra. Bulls*** he’s sick … that’s twice he’s (Kyrgios) done it,” he told the captain, who came out of retirement for Saturday’s doubles defeat following Kyrgios’ withdrawal.

The first time Tomic appeared to be referring to was Kyrgios’ decision to sit out of a Davis Cup tie against the Czech Republic in 2015 in his comment.

Watch video of the on-court remark below:

Tomic repeated his belief in a post-match press conference, in which he said he would “lose respect” for Kyrgios if he plays at the upcoming BNP Paribas Open at Indian Wells.

“It’s going to be really funny for me to see the next two days whether he plays or not, which I think he will,” Tomic, flanked by Hewitt, told reporters.

“I’m leaning towards just waiting to see whether he’s going to be playing in Indian Wells, that’s gonna tell me a lot.

“I’ve spoken to him already. If he plays Indian Wells, then he’s definitely lost a little bit of my respect.”

Several hours after Tomic’s claims, Kyrgios responded bluntly to his countryman on Twitter:

The answer to the hashtag’s question was Tomic, in 28 minutes. Kyrgios then deleted the above tweet and published these:

Tomic, who said Kyrgios told him he would “be better tomorrow”, fought back admirably to win the third set against Isner.

And he was well and truly in the match in the fourth set before eventually succumbing to the American’s red-hot serve.

“We all knew I had problems with my wrist,” he said.

“I came here, I had pain today a lot. In a situation where it wasn’t Davis Cup I would have pulled out, and not played today with the pain I was playing in.

“So in this situation today I pushed through, I played, but I’m just going to be really, really interested if he (Kyrgios) does actually (play).”

Australia must win a World Group play-off in September to stay in the top tier of the Davis Cup next year.

How this affects Tomic and Kyrgios’ friendship – and what reaction the former will provide – remains to be seen.

But Tomic, at the end of his press conference, said that the pair still shared a “good relationship”.

The pair have stood up for each other in the past, with Kyrgios vehemently defending Tomic against criticism from Australian tennis legend Pat Rafter.

Rafter accused Tomic of suffering from a “sense of entitlement” following an extraordinary rant at Tennis Australia following his Wimbledon exit.

Tomic was ruled out of a Davis Cup tie as a result.

Hewitt caught in the middle

After Tomic had sounded off, Hewitt contradicted his player and maintained that Kyrgios was “no doubt” sick.

“We ruled Nick out. He [Kyrgios] came down here, he gave everything he had to try and put his hand up to be available,” he said.

“There’s no doubt he was sick, absolutely no doubt.

“We did a fitness test with him on Thursday morning. He was ruled out by the medical staff.”

While Hewitt was forced to play against the US, his biggest test as captain may come as he tries to help Tomic and Kyrgios mend their friendship.

He also has a key role to play in their development, with both players publicly – and repeatedly – stating the respect and admiration they hold for the veteran.

Not Kyrgios’ first controversy of the day

Earlier in the day, the outspoken Kyrgios attacked New York Times tennis writer Ben Rothenberg on Twitter.

Kyrgios did not clarify what exactly caused him to send the tweet.

However, some suggested it was in response to a column by Rothenberg, which suggested Hewitt that would be selfish if he played singles on Sunday instead of Sam Groth.

The remarks from both on Sunday were the latest in a long list of incidents the pair have been embroiled in.

In 2015, Tomic was arrested for a disturbance at his hotel room in Miami, while in 2013 his father, John, was given an eight-month suspended jail sentence for headbutting his son’s then-hitting partner Thomas Drouet.

Kyrgios’ indiscretions include his “Kokkinakis banged your girlfriend” sledge towards Swiss player Stan Wawrinka in 2015, and a series of on-court fines and reprimands for angry outbursts.

– with ABC