It's a significant boost for the Gunners. In their midweek clash with Besiktas, the team looked as if it needed an injection of fresh talent. Welcoming back three World Cup winners is certain to lift morale and cause an upturn in performances on the field.
The availability of Mertesacker is particularly welcome. With Thomas Vermaelen having left to join Barcelona, Arsenal have been very light at the back. In Mertesacker's absence, teenager Calum Chambers has been pressed into immediate action alongside Laurent Koscielny. Although Chambers has generally acquitted himself well, his inexperience has occasionally been evident. Mistakes are inevitable while he learns the role.
Mertesacker's return will bring intelligence, leadership and a sense of calm to the Arsenal back four. With Mikel Arteta suffering with an ankle injury, the giant German will take up the captain's armband, too. Mertesacker will immediately become a figurehead of the team, and his status is only likely to grow across the course of the season.
The same is true of Ozil, who endured an up-and-down first campaign in English football. When he first debuted, his impact was immediate and impressive. However, he faded as the season wore on. The rigours of the Premier League took their toll on a player who was not used to that kind of relentless physicality.
However, Ozil ought to be fully acclimatised to English football now. Earlier this summer, manager Arsene Wenger passed up the opportunity to sign Cesc Fabregas to ensure he could bed in Ozil as the creative hub of his team. Now, it's time for the German playmaker to repay that faith. He has the talent but must now show the requisite temperament and tenacity.
Ozil and Mertesacker are sure to be major players for Arsenal over the coming months. However, if reports are to be believed, the third member of the trio could soon be heading for the exit. According to Sam Adams of Mirror, Podolski is edging towards a move to Turkish team Galatasaray:
Arsenal have reportedly told Galatasaray they will sell them forward Lukas Podolski, but not Joel Campbell.
Galatasaray wanted to sign both players in a £22m deal, but the Gunners are reportedly only prepared to let Podolski go.
Arsenal have told the Turkish giants they are willing to offload the 29-year-old Germany international before the transfer deadline, the Sun reports.
Podolski has become a fans' favourite since arriving at the Emirates from Cologne for £11m in 2011.
It is conceivable that Podolski could be allowed to leave. Arsenal are well-stocked for wide forwards. On the left-hand side, Santi Cazorla, Alex Oxlade-Chamberlain and even Alexis Sanchez are arguably ahead of Podolski in the queue for a first XI spot.
Will Lukas Podolski leave Arsenal in this transfer window?
The presence of Joel Campbell in the squad is another threat to Podolski's position. Wenger may decide there is only room for one left-sided striker in his 25-man squad. In that case, sticking with the younger man may make more sense. Podolski earns a hefty salary in London and could swiftly become little more than a very expensive reserve.
Arsenal's German trio could soon become a double act. Mertesacker and Ozil seem destined to become part of the furniture at Arsenal. Podolski, by contrast, could soon be loading up a removals van.