Conor McGregor is a high-level boxer and will cause Floyd Mayweather some problems, says Tony Jeffries

The former Olympic boxer Tony Jeffries has insisted that Conor McGregor is a “high level boxer” after watching the Irishman in a sparring session with Chris Van Heerden.

Two-weight UFC world champion McGregor will make his professional boxing debut against the undefeated Floyd Mayweather in Las Vegas on August 26, with the vast majority of pundits predicting a comfortable night for the 40-year-old.

Fears that the fight will prove uncompetitive grew when Van Heerden released video footage of his sparring session with McGregor.

The short clip – which quickly went viral – showed Van Heerden dominating McGregor, with the South African taking advantage of the MMA star’s clumsy footwork to land several clean shots.

McGregor’s performance in the video clip is so poor that Mayweather’s camp even speculated that the footage had been deliberated staged by the Irishman in an attempt to dupe his opponent into thinking he was a poorer boxer than what he actually is.

But Jeffries has said that the clip was not a fair reflection of the sparring sessions, which were actually far more level than the footage made out.

“I was there for the spar and have been there for many spars and they have been competitive, certainly not one way like everyone is making out,” Jeffries said in an interview on Sky Sports.

“People see McGregor take a punch and they jump on him. Van Heerden is a world class boxer though, always in great shape and McGregor gave him problems in there.

“If I came in and saw him sparring and never knew who McGregor was, I would think he was a high-level professional boxer, not a mixed martial artist or a novice boxer - I thought this guy can fight and box.”

Jeffries stopped short of predicting McGregor to win the contest, but said that his counter left-hand – recognised as the most dangerous shot in the UFC – will likely cause Mayweather some problems.

“The one thing that I was very impressed with when I saw him spar was his athleticism, his elusiveness and the way he comes back with that counter left hand,” he added.

“Even when not in training camp and at full fitness, he still has that potent weapon.

“I don't think he will beat Mayweather, I can't see that, but I think he's in there and it will be an entertaining fight.”