There was plenty of tension as Fernando Verdasco and Thanasi Kokkinakis went head-to-head over the Australian's father at the Miami Open.

Qualifier Kokkinakis, who stunned world number one Roger Federer earlier in Miami, went down 3-6 6-4 7-6 (7-4) to Spanish veteran Verdasco but not before tempers flared between the two players on Monday.

At a change of ends in the third and final set, Verdasco voiced his frustration about an individual in the stands, sparking a row involving Kokkinakis' dad.

Verdasco thought the person distracting him between serves was Kokkinakis' coach, the former world number seven told the umpire: "What I cannot accept is that the guy behind is talking in between the first and second serve.

"I know how it is, I've been playing professionally for 15 years, I'm not trying to disrespect him [Kokkinakis] or cut his rhythm or anything, but what I cannot do is not stand up and say anything. I cannot stay quiet if I cannot serve."

The situation agitated Kokkinakis as Verdasco responded, "I didn't mean to disrespect you, I was talking to him" as the Spaniard pointed to a man in the crowd.

Kokkinakis then said: "That's my dad, it's my dad so it's affecting me."

"No it's not your dad, it's the guy on the left, it's not your dad, sorry Thanasi, it's not your dad," Verdasco replied before Kokkinakis hit back, "Yeah, that's my f****** dad!"

Verdasco apologised before providing an insight into the verbal bust-up post-match at the ATP 1000 tournament.

"I was losing my focus because of this person talking between first and second serve and also in the third set when I doubled faulted and he started screaming and shouting supporting Thanasi so I told him to be respectful," Verdasco told Sky Sports. "I didn't mean to do anything wrong and Thanasi started talking to me when I didn't mean to disrupt him or try to lose his focus at all.

"I told him I'm sorry and I didn't know who this person was and actually it was his dad, I never met his dad before and I told him that I'm really sorry."

While Verdasco and Kokkinakis clashed on court, fellow Australian Nick Kyrgios was busy having his say via social media.

Kyrgios, who cruised into the last 16 with a win over Fabio Fognini, tweeted: "I hope TK [Kokkinakis] wins this match, Verdasco is the saltiest dude, must be frustrated at his past success against Aussies."

I would honestly have told it to Fernando’s face, the reason I deleted my previous tweet was because I didn’t want to cause unwanted attention, but I’m just gonna leave this here. Thanks for blocking me, I’m sure that took a lot of courage x — Nicholas Kyrgios (@NickKyrgios) March 26, 2018

It drew a response from Verdasco, who wrote: "When you have the courage to put a tweet insulting another player you need to have the same to don't delete it."

Kyrgios then returned serve, responding by tweeting: "I honestly would have told it to Fernando's face, the reason I deleted my previous tweet was because I didn't want to cause unwanted attention, but I'm just gonna leave this here. Thanks for blocking me, I'm sure that took a lot of courage x."