David Luiz has signed a new one-year contract with Arsenal, who have extended Dani Ceballos' loan and agreed to permanent deals with Pablo Mari and Cedric Soares.
A pre-season signing from Chelsea, David Luiz has endured mixed form with the Gunners and produced an error-strewn display in last Thursday's (AEST) loss to Manchester City before being sent off.
Despite that, technical director Edu described the experienced defender as a key player for the club, whose hopes of Champions League qualification suffered a further blow after Saturday's loss to Brighton and Hove Albion.
"David is a really important player for us," he told the club's official website.
"He has played most of our matches this season and has been important for the team.
"His passing, his communication with the team on and off the pitch. He helps everyone."
Fellow defenders Mari and Cedric will complete permanent moves from Flamengo and Southampton respectively when the transfer window opens next month on what the club describe as "long-term" deals.
Midfielder Ceballos, meanwhile, will remain on loan from Real Madrid until the end of the 2019-20 campaign.
Mari suffered an ankle injury against City and is set for at least a couple of months on the sidelines, while Cedric is close to making his debut after a facial injury.
Edu was delighted to retain their services, along with those of Ceballos.
"With Pablo we're all disappointed he got injured at Manchester City," he said.
"Since Mikel [Arteta] arrived here he was asking for a central defender who was left-footed.
"We were really pleased with Pablo - his behaviour, the way he is training, his mentality and his quality. Unfortunately, he has that injury but of course we are really happy to keep him for the future.
"Cedric is also going to be an important player. He has been unlucky with the injuries but he is close to being ready and gives us more strength in the right-back position.
"We're also pleased Dani will finish the season here. He is making a good contribution and we look forward to him having a strong finish to the season."