The Red Devils suffered a surprise 2-1 loss to Championship side Bristol City in the League Cup quarter-final at Ashton Gate on Wednesday night.
Manchester United have lost two of their last four games in all competitions, while securing narrow victories over Bournemouth and West Brom.
The 20-time English champions lost 2-1 to Premier League leaders Manchester City in the derby clash at Old Trafford to leave Manchester United 11 points adrift of their neighbours.
The Red Devils will take on a Leicester side that have collected 17 points from a possible 27 under new manager Claude Puel.
Former Arsenal midfielder Merson is tipping Manchester United to return to winning ways at the King Power Stadium despite their mid-week disappointment in the League Cup.
“Football is weird, isn’t it?” Merson told Sky Sports. “Bristol City beat a strong Man Utd team in midweek after Crystal Palace had hammered in-form Leicester.
“United are better than what they are showing. There is still a lot more to come from them.
“Teams like Leicester have to work so hard to win a football match, and the match against Man City in midweek will have taken a lot out of them.
“These top teams can play in second gear and win a football match. This just feels like one of those games.”
Manchester United finished in sixth place in the Premier League table last season to miss out on a European spot.
However, the Red Devils managed to secure a return to the Champions League following a 2-0 victory over Dutch giants Ajax in the Europa League final.
Manchester United were 3-2 winners against Southampton in the League Cup thanks to Zlatan Ibrahimovic’s goals either side of half-time.
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