Roberto Firmino has returned to Liverpool training ahead of the EFL Cup third-round match with Derby County on Tuesday, coach Jurgen Klopp confirmed.

A groin strain made Firmino, who struck twice in the 4-1 win over defending Premier League champions Leicester City on September 10, unavailable for the 3-1 victory over Chelsea that followed on Friday.

The Brazilian may not be risked for the trip to the iPro Stadium, with Klopp not interested in resting players when they are fully fit.

"In my opinion we only have strong line-ups. That's good news. We will find a strong line-up. We won't rest 100 per cent fit players," said Klopp.

"No decisions [on the line-up have been made] yet as the session this afternoon [Monday] will be important, but Firmino is back in training.

"We gave him yesterday [off] because the medical department suggested it. He could have played but I decided against it. They told me if we give him three days off it will be perfect. Today is the fourth day.

"It's all about taking risks in football, but not with players who are not 100 per cent."

Mamadou Sakho has not featured for Liverpool since being sent home from the pre-season tour to the United States for breaking rules three times.

The centre-back remains short of fitness, but according to Klopp that will not be the key factor in determining when he is ready for selection.

He added: "He's still working on his fitness. It's a big difference to being match fit. It's not about how the player feels, it's about how I feel. It's a long, long time since he played."

Joel Matip has stepped up in the Frenchman's absence and Klopp has been delighted with the start to his Liverpool career.

"If you lived or worked in Germany you would have known much more about him. It was pretty clear it would make sense to sign him," said the German. 

"He needed to work on his fitness but there was never a doubt over his quality. It's very important because of the situation in the centre-back position."

Liverpool were runners-up to Manchester City in the competition last season and Klopp wants to go one better this term.

"We don't think about what league our opponents are in. We want to win this competition. This is our next step to do it," Klopp said.

"I watch a lot of Championship football. Derby are an ambitious club. We have a really competitive game against a strong side.

"It's not about speaking about trophies. Everyone knows we are ambitious but it doesn't help to talk about it."