Thanasi Kokkinakis says it wasn’t so much the alleged tank, but more the strange manner of it, that has put Nick Kyrgios in the firing line with tennis fans – and potentially officialdom.

One of Kyrgios’s closest allies, Kokkinakis says “tanking” – tennis terms for not putting in 100 per cent effort – is not an uncommon occurrence during matches, with players sometimes happy to let a game or two go if they feel it’s a lost cause chasing a set.

But Kokkinakis says it’s usually done fairly subtly.

Kyrgios appeared to virtually stop competing in the third game of the second set of his 7-5 6-1 6-7 (7-9) 7-6 (8-6) fourth-round Wimbledon loss to Richard Gasquet on Monday.

Under grand slam rules, Kyrgios could technically face a $US20,000 ($A26,675) fine if found not to have given his “best effort”.

But the fact he received no warning from the chair umpire and fought back from two sets down to almost push the match into a fifth and deciding set indicates the young firebrand will likely escape sanction.

Kokkinakis, who won the Wimbledon junior doubles crown with Kyrgios in 2013, admits his friend’s apparent one-game tank “wasn’t too surprising because I know what he’s like”.

“Tennis can be a very frustrating sport sometimes and obviously he lost it a little bit there,” Kokkinakis said.

“I mean, I haven’t done it to that level, just leaving balls. But if you’re down 4-0, 40-love, you probably don’t hustle so hard for the next ball.

“I’ve seen it done before where players, when they win like a tight third set and they go down a break in the fourth set, they can conserve energy for the fifth.

“It happens pretty often, but it’s just how you go about it, I guess.”

Kyrgios, who only turned 20 in April, denied tanking but attributed his play at that time to grand slam pressures and being unable to find the level required to challenge the red-hot Gasquet in the opening two sets.

“I’m getting frustrated myself,” he said.

“I feel as if I’m playing not how I should be playing. I’m angry at myself.

“It’s an opinion, I guess. If they decide to fine me, they can fine me.”