News'Arthur has been first-class and wants to build up his fitness'
The on-loan Brazilian went the full distance during Saturday's Premier League 2 win at Leicester City and then played for just over an hour in the Papa Johns Trophy tie with Rochdale on Tuesday night.
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"Arthur has been in over the international break to play games and build up his fitness," Lewtas told the Liverpool Echo.
"That's off his own back, so that shows his level of professionalism. He has been great with the lads as well. He has been first-class.
"In training on Monday he was excellent, he really drove the lads and as a matchday minus one, it's probably the best one we've had.
"He wants to get fit, he doesn't need a week off, so it's come from him.
"He doesn't speak Scouse and I don't speak Portuguese, but I think you can tell from the body language. In the meetings we went through some extra things and cleared a few things up. He has embraced it.
"He first trained with us on Friday. He trained with the first team and then he had a session with us for the team that was going to play against Leicester.
"He'll do a little work with us during the international break."
Stefan Bajcetic also featured in a holding midfield role during the U21s' 1-0 loss to the League Two side in midweek.
Due to international call-ups for a number of young players, Lewtas had to experiment at the back with midfielders Luca Stephenson and James McConnell filling in at centre-back and right-back respectively.
"I thought Stefan was excellent," Lewtas said. "As a number six, we were able to play through him, I thought we built really well.
"Obviously Arthur and Stefan will grab the headlines but Dominic Corness wasn't the weak link in there.
"We had three ball-playing midfielders, and Dominic dropping to the sides – I thought he was superb. He was at the hub of how we built and from a midfield point of view, we were really good.
"Luca was excellent at centre-back. He's a good footballer, he understands the game and dealt with a couple of senior number nines really well.
"James is an attacking midfielder, so to play him at right-back against an out-and-out wide player, I thought he did ever so well."
Lewis Koumas, who turned 17 on Monday, made his debut at U21 level when he started the game due to Jake Cain picking up a knock in the pre-match warm-up.
The eight-goal forward played on the right side of the attack, supporting Layton Stewart and Harvey Blair.
"Lewis did well, given he'd only been told in the warm-up that he was playing," Lewtas continued.
"I was a little bit worried because we had players in different positions and you hope it comes together but I thought we did well.
"I'm really disappointed actually. Rochdale started great but we weathered that storm. I thought we were really good but we probably weren't quite able to make up the distance from building up play to attacking. We couldn't get enough bodies around the ball."
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