The Gunners have bolstered their ranks with the signings of Granit Xhaka and Rob Holding, but have seen the likes of Manchester United, Liverpool and Manchester City make a host of marquee signings.
And Mertesacker, 31, admits this is a cause for concern for the upcoming season after claiming it was a miracle the Gunners finished second last term.
“The way last season went, we were quite lucky to finish second," said Mertesacker.
GETTY
Per Mertesacker looks on during an Arsenal training session
“We turned things around at the end but it was kind of a miracle we finished runners-up.
“What really disappointed us was that Leicester were able to take advantage of all the other big teams suffering and we couldn’t do the same.
“That will be a big motivation next season — to keep up with all those good teams who finished behind us.
“Of course, those big clubs will be stronger this time. That’s what I expect as they’ll start the season with a lot of new players.
“A lot of transfer business has already been done and it won’t be easy for us this time, especially with all the signings going to the other clubs.
“So we also need to be stronger and I am looking forward to seeing how well we compete for the title with not a lot of signings and a lot of young players.”
Having spent £30m on Xhaka, Arsene Wenger is still looking to sign attackers after missing out on Jamie Vardy and is now reportedly eyeing a move for Riyad Mahrez.
Wenger insists he will spend big again if he can get the right players to the Emirates, but Mertesacker accepts that simply breaking the bank is no longer guaranteed to bring success.
“You cannot predict what will happen with the other teams. Even when you have bought three or four big players, you still need to complement each other," he added.
“So there are still a lot of questions to be answered.”
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