The north London club are currently without the first choice Francis Coquelin, who is expected to be out of action until March due to a knee injury.
Mathieu Flamini has been filling in for the injured Coquelin in recent weeks and Arsene Wenger moved quickly to bolster his squad with the addition of Elneny this month.
However, former Gunner Merson feels that the north London side are still short in that position – and also wants to see Arsenal sign a new central defender before the January transfer window closes.
Speaking on Sky Sports News HQ on Thursday morning, Merson said: “I still think they need a world-class holding midfielder or someone better than what they have got and the other thing they need is another defender.
“If you watched the defending on Wednesday, you cannot go away to Liverpool who, let’s be honest, did not play really with a centre-forward, or at least a centre-forward who is a massive threat.
“So for me, I think a centre-back is needed badly and watching that game, you were thinking; ‘What would Messi, Neymar and Suarez do to them?'”
Arsenal, who drew 3-3 at Liverpool on Wednesday, are currently top of the table on goal difference heading into Sunday’s testing Premier League clash at Stoke City.
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