Alan Smith believes that Arsene Wenger has seriously missed out after not signing Gary Cahill in the summer, after the defender joined Chelsea last week in order to help the Blues maintain their advantage over Arsenal for a Champions League spot.

The Gunners had a particularly difficult summer last year, losing two of their top players in Cesc Fabregas and Samir Nasri.

While the club went on a spending spree in the final 24-hours of the transfer window, purchasing five players before 11pm hit the clock, Arsenal were unable to seal a deal for Cahill.

Wenger admitted later that Bolton had asked for an excessive fee their star, and with Cahill only having a year left on his contract, the Frenchman wasn't willing to pay over the odds for the England international.

Instead, Arsenal went with Per Mertesacker, and the former Highbury hero believes it was one of their biggest mistakes in the last transfer window.

"With the Cahill thing, we don't know exactly how it happened but we do know Arsenal made a bid which Bolton rejected, so why not go a bit higher, pay the asking price and get the player?" He told Talksport.

"Now he's gone to Chelsea and he's a good signing for them, and he would have been a good one for Arsenal, and better than Per Mertesacker, in my opinion.

"Cahill knows the league, he's an England player and he could be an England player for the next few years and would have had a good re-sale value even at 30.

"Sometimes Wenger thinks clubs are asking too much and that he wouldn't get a return. It's almost like it's his money and he's careful how he spends it."

Cahill will now play for Chelsea, after the west London club agreed a reported £7 million fee for the 26 year old at the start of this month.

And Smith revealed he thinks that Wenger did not prepare adequately for last summer's transfer window, leaving him without options as he signed the likes of Mikel Arteta and Mertesacker.

"They did seem like panic buys at the 11th hour," he explained.

"Arteta is 29 with an injury record, something Wenger looks at; Benayoun is 31 and won't make a huge difference to the first XI at the Emirates.

"Mertesacker has 80 caps for his country but doesn't look a player who has that. Ask him to run and he looks slow and it's worrying .

"He's a good solid character, but that's not always enough.

"Getting into the top four this season would arguably be Wenger's greatest achievement. They've got players coming back [from injury] who will make a difference, but if they keep defending like they are at the moment they will be going nowhere."