And he has backed his WBA bantamweight champion sibling to make a big impression on British boxing’s latest big fight night.
Doncaster fighter Jamie will face Fernando Vargas at the O2 Arena in London tonight, on the undercard of Anthony Johsua’s bid to become IBF world heavyweight champion.
It comes after what became a 20 week camp working under trainer Dave Coldwell, with whom he joined forces last year.
And Gavin says the work both he and his brother have been put through by Coldwell has been invaluable.
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“It’s been the little things we’ve been learning that have made the difference,” super bantamweight contender Gavin said.
“But you see them when you’re in there sparring and it makes things a lot harder.
“I’m noticing with our kid the way he’s holding himself, keeping his shape and that he’s a lot harder to hit.
“I think you’ll see a big improvement our kid in this next fight.
“It’s also with him having longer camps. It’s not just chucked on him with six or eight weeks to go.
“He’s not towing with the weight. He’s flying and his weight won’t be a problem.
“His last two performances were phenomenal but I think the homecoming here will be a standout performance.
“We’re both flying.”
It is a sentiment shared by Jamie as he heads into the fourth defence of his WBA crown.
McDonnell says he feels ‘a million dollars,’ partly due to the work of nutritionist Dave Stache, who co-owns healthy fast food restaurant Nourish in Sheffield.
He said: “Usually I’d be desperate to get the weigh in out of the way so I could get some proper food in me.
“I’d have been craving all sorts of stuff for a long time.
“But it’s not like that now. I’m eating and I’m eating well all through the camp and I’m making weight better than I ever have. Dave takes care of it all so you basically pick it up and eat it.
“I think you’ll see the difference when I get in there.”