Speaking after Sunday's FA Cup fourth round win over Brighton and Hove Albion, Arsenal boss Arsene Wenger told BT Sport: "It's very, very, very close and it should be done tomorrow."
Asked about the qualities that defender Paulista, whose move will coincide with Joel Campbell going the other way on loan, will bring to the squad, the Frenchman added: "He is 24, a good size, good pace and a good defender of course.
"He's played for only one year in Europe, so maybe there are things to work on, but the potential is there."
Paulista - who plays at centre-back and is rated at around £15million - will join a side on a four-match winning run after goals from Theo Walcott, Mesut Ozil and Tomas Rosicky secured the holders a place in the last 16 of the FA Cup.
Walcott was making just his second start of the season, while Ozil was in the starting XI for the first time since October, and Wenger was full of praise for the duo following the 3-2 win.
"They've done well for players who've been out for such a long time, it was a pacy game on a difficult pitch," he said, before turning his attentions to the defence of a trophy Arsenal won by beating Hull City at Wembley last May.
"We'll have a go of course but there's such a long way to go and you've seen again that a tie is never predictable, you have to fight for it. We are ready for a fight so we'll have a go."
