Former Arsenal defender Per Mertesacker believes David Luiz can "learn from his mistakes on the pitch", but claims the centre-back is "comfortable" at the Emirates Stadium, following his move from Chelsea.
The Brazil international, 32, was at fault for two of Liverpool's goals during their 3-1 defeat in August, conceding a penalty which Mohamed Salah scored.
He also pulled out of a challenge on Salah because he was on a yellow card, which resulted in the Liverpool forward scoring a fine solo goal in the 58th minute in the game at Anfield.
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Mertesacker, who is Arsenal's academy manager, says: "I think he (David Luiz) will learn from his mistakes on the pitch, but he is very comfortable being at Arsenal.
"That's what I have been seeing. So we are happy to have him.
"He brings something different to the table right now. So I think he is able to learn and excel his level of being an Arsenal player."
The former Chelsea defender has started in three of Unai Emery's side's Premier League games this campaign.
'We have a lack of balance right now'
Arsenal have both conceded and scored six goals after two wins, one draw and one defeat in their opening four games of the Premier League season, leaving them fifth in the table.
Mertesacker believes the team's formation and the role of the front three Pierre-Emerick Aubemayang, Alexandre Lacazette and Nicolas Pepe needs more clarity if they are to give away fewer goals.
He added: "I think we have a lack of balance right now. Where you feel like, ok we have amazing strikers but they as well need to understand that we need to have a certain compactness.
"It's not only about us three (lead) strikers providing an offensive threat. It is about these front three as well, leading the first frontline as being a defensive unit.
"So I think we need to be cautious of that. No matter how much striking power you have got, you need to have a sense of defensive compactness from everyone.
"So it's not only the back four who should be judged on how many goals we concede."
Watch Watford vs Arsenal on September 15 live on Sky Sports Premier League from 4pm; kick-off 4:30pm.