The pair have put themselves through the mill with some tough sessions while preparing for Super Rugby Pacific.
"I was crying in one of them, that's how hard it was. I never cry in a session. He wasn't crying, he was laughing," Clarke said.
Just how hard they have worked was evident in Clarke dropping his weight by 4 kgs to 104kg. But his strength, and power, had not been impacted, he said.
He also helped Tuivasa-Sheck develop his passing game, with the league champion also calling on Danny Tusitala, his brother Johnny, and cousin Vince.
"That's where we built our relationship," Clarke said.
"Rugby-wise, we sat down together every morning just talking through different pictures. That was when it was just us two, but now he's got all the coaches and boys like Stephen [Perofeta] and Harry [Plummer].
"He's growing in the game. He's helped me with my footwork. It's helped me on attack but I don't think it's helped on D [defence], I'm still getting stepped. But, it's been cool having someone of his calibre here at the Blues," he said.
The ruck area had been a work-on for Tuivasa-Sheck, especially getting over the ball in the jackal.
Clarke said Tuivasa-Sheck would provide some tough decisions for the selectors and only increase the competition for places in the side, but that would bring the best out of them.
Clarke said last year his attention had been divided. Being in lockdown for so long, and being dealt several bad hands in terms of opportunities, made him realise there was more to life than rugby.
"So this year has got one focus and that is enjoying rugby. It's been awesome being back with the boys," he said.
"I'm here, and I'm enjoying myself, and that's the most important thing you want to do when you play sport as a career, just making sure you come in every day enjoying it and loving the game.
"I've found that love again. If I look back, I put too much expectation on myself. I listened to too many people, where I should have been listening to my small circle and enjoying the game.
"I'm not worried if I don't make the All Blacks, or Sevens or anything, I just want to enjoy the game," he said.
Missing the Olympic Games had been disappointing, but he had no regrets and missing out on both that and the All Blacks end of year tour had provided him with lessons on how he could deal with things better.
"I haven't played any form of rugby since June, and I come in every day with itchy feet [to play].
Coping with the various demands imposed by Covid-19 was something the players had become used to heading into their third season under restrictions.
He was thankful he could be with people instead of being locked down. Clarke felt he thrived most when he was around people.
Clarke said they were coping with whatever Covid brings. It was a day-by-day scenario at the moment.