Gabriel, 24, had a work permit agreed earlier this week and arrives in England with Joel Campbell, who also signed a new long-term contract, moving from the Gunners to the La Liga side on loan until the end of the season as part of the deal.
Though born in the southern city of Sao Paulo, Gabriel learned his trade with Esporte Clube Vitoria in Bahia, north east Brazil. The academy product was promoted to the club's first team in 2010 and soon found himself dropped in at the deep end, playing out of position at right back against a Neymar-led Santos in the 2010 Copa do Brasil final. Vitoria lost 3-2 over two legs; Neymar scoring one of the goals and missing a penalty.
For most of this season, Arsenal have had an imbalanced squad.
Some of that was down to the fact that players were missing through short-, mid- and long-term injuries. However, when you looked at how the squad was constructed in the summer, it boiled down to the fact that the Gunners had too many attacking options, and not enough defensive depth.
So far this January, three forwards who hardly featured have left the club on loan. Lukas Podolski went to Inter Milan, Yaya Sanogo to Crystal Palace...
Welcome to the second edition of Insider's Premier League Forecaster, an end-of-season table projection fueled by ESPN's Soccer Power Index (SPI), a regression-based algorithm designed to predict soccer matches. SPI simulates the remainder of the season 10,000 times, using the odds of each projected match, with the end result presented in the table below.
If you missed the inaugural version two weeks ago, click here for a primer and the previous table. (Note: The previous table forecast was incorrect due to a projection error. Chelsea, not Manchester City, should have been the projected favorite to win the league leading up to matches Jan. 10.)
With a lull in Premier League action last week due to FA Cup and Capital One Cup matches, in this edition we break down table risers and fallers over the past few weeks and preview what promises to be one of the most important matches of the season: Chelsea versus Manchester City on Saturday.
Here's a look at the latest forecast for all 20 Prem teams, along with breakdowns of the title, Champions League and relegation battles.