The Germany defender has been keeping a close eye on his fellow Gunners when the 'Nationalmannschaft' has not been in action - and had particular praise for Walcott's stunning substitute appearance against Sweden.
"I'm very pleased for Theo and Alex," Mertesacker told Arsenal.com. "They were both in and out of the team, but then Theo scored and it was a special moment - it always is when you have to wait for your chance and then play like that.
"He showed that he's a great player, having had a great season for Arsenal. I think it's a great thing when you are not in the starting line-up but are able to show your full strength and take your opportunity. He showed that he is very confident."