Arsenal have been warned they are ‘missing something’ after letting two key players leave the club in the summer.It follows their shock Carabao Cup exit at the hands of League Two side Fleetwood Town.Arsenal’s loss to Fleetwood highlighted a transfer mistake, says Jamie O’HaraGettyThe Gunners were beaten on penalties at Highbury Stadium on Tuesday night after labouring to a 1-1 draw in the fourth round.Their defeat was the first for the reigning champions of England to a fourth-tier side in the competition for 52 years.Ex-Tottenham midfielder Jamie O’Hara believes Arsenal’s struggles against Fleetwood stemmed from the sales of Leandro Trossard and Gabriel Martinelli.The pair were allowed to leave the club for Besiktas and Al Hilal, respectively, in the summer.It came despite the duo providing a combined 37 goals and assists across all competitions last term.Arsenal’s transfer mistakeFollowing Arsenal’s penalty shootout defeat, O’Hara was joined on The Sports Bar by Gunners fan Francis.During their discussion, the talkSPORT co-host explained: “I’ve been watching you this season and, look, you know how to win in Premier League games.“I’m not convinced. I feel like you’re missing something. I feel like you’re missing Trossard a little bit, even Martinelli.“I feel like you’re missing someone who can just come up with something special out of nothing.”Trossard departed for Besiktas in July for a £16.7million fee despite his 11 assists for Arsenal last season.Arsenal have been warned they were wrong to sell Martinelli and TrossardGettyThe Belgium winger was tied with Declan Rice for the most of any Gunners player across all competitions.Meanwhile, only Viktor Gyokeres scored more goals for the club than Martinelli, who ended the campaign with 11 to his name.The 25-year-old joined Al Hilal for £55.2million at the end of the transfer window.Arteta’s selection headacheDespite signing Christos Tzolis following Trossard’s exit, Mikel Arteta appears short of options out wide this term.Both Tzolis and Bukayo Saka are currently sidelined through injury, leaving Noni Madueke and 16-year-old Max Dowman as the only first-team wingers.However, Madueke was not included in the matchday squad against Fleetwood.Arsenal opted to sell Trossard to Besiktas in JulyGettyInstead, Dowman started on the right, with 18-year-old striker Ceadach O’Neill making his debut on the opposite flank.O’Neill was ultimately replaced by Eberechi Eze after 66 minutes.Meanwhile, Dowman was sent off with five minutes left of normal time.As a result, the teenager will be suspended for Arsenal’s upcoming Premier League matches against Liverpool, Hull City and Newcastle United.It leaves Madueke as the only recognised wide player available to Arteta for those fixtures at present.Dowman will not be cleared to return to the side domestically until the visit of Manchester City on Sunday, November 29, although the Gunners are expected to appeal.