Wrexham must land an upgrade on Jacob Mendy this summer who would be perfect for Phil Parkinson’s system. The transfer window isn’t even open yet but Wrexham have faced the harsh realities of competing for players in League One. Phil Parkinson wanted to sign centre-back Jason Kerr from Wigan Athletic, though the 27-year-old snubbed the Reds and signed a new contract with the Latics. Rob McElhenney and Ryan Reynolds also reportedly placed a ‘big offer’ on the table for Conor Hourihane however, the ex-Derby midfielder instead joined his former club Barnsley in a player/coach role. Losing out on …