The Gunners defence has struggled in the 2017-18 season so far after conceding 20 times in 18 games ahead of the visit of Liverpool FC.
Arsene Wenger has switched between a traditional 4-4-2 and 3-4-3 in the Premier League in the current campaign.
Laurent Koscielny has been a rock at the back for the north London club but Monreal and Mustafi have struggled to match the France international’s performance level.
The 30-year-old has been without a consistent centre-half partner since Per Mertesacker’s regression to leave Wenger short on options at the back.
Former Republic of Ireland international Breen, who is a self confessed Arsenal fan, warned that Monreal and Mustafi aren’t up to scratch.
“Monreal isn’t good enough at centre-half for an elite level club,” Breen told Irish radio station Newstalk.
“I don’t think Mustafi is good enough for Arsenal despite costing 35m and being a German international. Koscielny has struggled because.”
Arsenal haven’t won the Premier League title since 2003-04 when Wenger had the likes of Kolo Toure, Sol Campbell and Martin Keown to call upon at centre-half.
The Gunners signed Mustafi in a £35m deal from La Liga giants Valencia in the 2016 summer transfer window to improve their defensive options.
Arsenal have won the FA Cup three times in the past four seasons to at least win some silverware.
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