"This is almost done," is the message from Ball's corner as they try to stem the flow of blood.

Ball dabs away the blood as it continues to pour from his nose, steps forward and lands a one-two followed by a hook.

A big round for Ball to get the momentum firmly back on his side.

The second half of the fight is off to a fast start.

It looked like a left hook that sent Rios down.

The American suggested it was a slip, I thought it looked like one, but it counts as a knockdown.

Ball senses Rios is there for the taking and turns up the tempo.

Rios is down for a second time!

Despite warnings from the corner, Rios eats an uppercut and then goes searching for one of his own, but it's blocked off the gloves by Ball.

A couple of warnings from referee Bob Williams - one for use of the head and one for holding.

Rios spins off the ropes but Ball is straight on his heels and lands with a right as the American turns back to face him.

Image source, Queensberry Promotions

Paul Smith
Retired boxer on BBC Radio 5 Live

Nick Ball is probably looking a bit more tired than he is because his nose is so badly injured.

A lot of fighters breathe through their nose, if your nose goes it's very difficult to then change the way you breathe and your system.

Ball has definitely slowed down a little here. He threw so much into the first three rounds and earned a knockdown, but how much has that taken out of the champion?

Is this a risky gameplan that's starting to pay off for Rios?

Rios might just have taken this round and the blood is pouring from Ball's nose. That is messy!

Image source, Queensberry Promotions

Ball had it all his own way through the first three rounds but Rios started to find a rhythm in the fourth and is growing further into the fight in this round.

Ball's hands are low and Rios punishes him with a right hook.

A left to the body from Rios also lands.

We've got a fight on our hands.

Josh Warrington
Former world champion on BBC Radio 5 Live

Every time Rios looks like that's it he's going to go down, he's going to take another knee or he's going to throw the towel in, he just battles back and digs right down into the depths of his stomach and he pulls a little combination to keep Ball on his toes.

"He's trying to counter you with the left hook or uppercut, be careful of that."

Wise words from the corner of Rios as they prepare their fighter for round five.

The speed of Ball is something to behold.

Some great combination work from the champion and then he changes the angle before unloading again.

Ball is varying his attack and a left uppercut sneaks through.

Rios steps forward and is caught on the counter.

Ball has more blood streaming down from his nose. It's not clear if that's a new cut or the same one from round two.

Image source, Queensberry Promotions

How much longer will this go?

If Rios doesn't start to come up with some answers then the referee might just step in.

A firm left hook sends Rios stumbling back to the corner.

Rios walks back to the centre and Ball urges him on. Rios is starting to throw a little bit more but he's not having a great amount of success.

Paul Smith
Retired boxer on BBC Radio 5 Live

Nine minutes of extreme high-pace work rate.

Ronald McIntosh
Commentator on BBC Radio 5 Live

Nick Ball will simply not leave him alone.

Rios has some blood under his left eye.

Ball stumbles as he throws everything into the attack but he's quickly back on two feet and offloading everything.

Referee Bob Williams is watching closely as Ball backs Rios into the corner.

Williams is thinking about stopping it until Rios escapes and the bell rings.

Image source, Queensberry Promotions

Paul Smith
Retired boxer on BBC Radio 5 Live

You've got to be a tough man to keep this for 12 rounds and you've got to be a fit man to keep this going for 12 rounds.

This could be over very quickly.

Ball came out with his foot on the gas in this round and Rios' defences are no longer standing as firm.

Ball is relentless in his pursuit of the American.

Ronald McIntosh
Commentator on BBC Radio 5 Live

I'm keeping a close eye on the bridge of Nick Ball's nose because it's reddening and I'm just seeing whether there's any blood leaking from the nose.

The pressure tells.

Rios is down from a short left hook after a barrage of punches!

Rios covers up and invites Ball to come forwards - Ball accepts that invitation but is struggling to land clean punches through the guard.

Some are making contact but the majority are bouncing off the gloves. Ball is a bundle of energy but will he punch himself out?

It's one-way traffic.

Ball has some blood on his nose as he returns to the corner at the end of the round. I didn't see a punch land from Rios so it may have been a clash of heads.

Image source, Queensberry Promotions