Arsenal have not won the Premier League since 2003-04 as pressure grows on Wenger to end that drought at the Emirates Stadium.
Former Arsenal midfielder Merson, who also played under Redknapp at Portsmouth, claims the 70-year-old is tactically superior to his French counterpart.
"People say Redknapp's a wheeler-dealer and it's so disrespectful," Merson said via Sky Sports' A League Of Their Own.
"Tactically, he's one of the best I've worked with.
"If Arsene Wenger had Harry Redknapp's tactical nous, Arsenal would win the league."
Arsenal are fifth in the Premier League, six points adrift of leaders Manchester City following a slow start to the season.
Wenger's men travel to Watford on Sunday after the international break.