Chelsea have propelled Arsenal in the Premier League title race with the sale of Petr Cech to their London rivals, according to former defender Graeme Le Saux.
After falling behind Thibaut Courtois in the pecking order at Stamford Bridge after 11 years at the west London club, Cech has moved to the Gunners on a long-term deal for a reported £10m ($15.5m), according to The Guardian.
Chelsea manager Jose Mourinho says the club's owner, Roman Abramovich, sanctioned the exit, which will see Cech go directly into the Arsenal first team from next season.
Wojciech Szczesny and David Ospina were rotated last season, with the former playing in the FA Cup final win over Aston Villa.
Ospina, meanwhile, finished the campaign as the club's number one in the Premier League but Wenger has decided to freshen up his options in a position that has proven to be problematic for Arsenal.
And, according to Le Saux, despite finishing eight points ahead of Manchester City, and 12 above Arsenal on their way to claiming the league title, Chelsea have allowed Wenger's side into the title race.
"It was a very grown up thing for Chelsea to do," he told Sky Sports. "It shows the huge respect they have for Petr. He still has a massive amount to offer and they were willing in the end to sell him to one of their main rivals.
"So that's Chelsea repaying his loyalty to the club as he was the best 'keeper in the Premier League, if not in the world, for a long period.
"He's a fantastic ambassador for the sport as well and he's still got a lot to offer, so he's a great signing for Arsenal too.
"He's in a key position for them. Arsenal have strengthened their squad, still have a few positions to fill, but are title challengers."