Former Chelsea midfielder Ray Wilkins says Petr Cech could help Arsenal in their quest to win the Premier League title.
The 33-year-old is set to become Arsenal's first summer signing after undergoing a medical at his new club.
He will take over from David Ospina who will leave the Emirates to join Fenerbahce in Turkey.
"I'm extremely surprised and I thought Chelsea might have offloaded him into Europe somewhere," Wilkins told Sky Sports News HQ.
"He's been a fantastic servant for the club and the service he's given the club has been unbelievable.
"I think [Chelsea have] done him a favour.
"Whether they've done themselves a favour is another question because with Petr going to Arsenal it reinforces their ability to be contenders for the Premier League title.
"I'm slightly surprised Chelsea have allowed him to go to another Premier League club.
"I think Petr will give a great deal to Arsenal and it's Chelsea's loss. I'm pleased we'll get to see him in the Premier League week in, week out now.
"It is absolutely a bargain.
"Bearing in mind he never played last year, so in football terms he's 32, not 33. He's got eight years left at the top level."