Top-flight Fulham were in danger of losing to visiting Championship (second-tier) team Sunderland but salvaged a 1-1 draw thanks to Tom Cairney’s equaliser at Craven Cottage.
Southampton put their Premier League woes aside to beat Championship strugglers Blackpool 2-1 while Bristol City eased to a 3-0 win over fellow second-tier side West Bromwich Albion.
Leicester, who beat fourth-tier strugglers Gillingham with an Iheanacho goal in round three, faced a stern test from a hard-working, high-energy Walsall outfit.
It took 30 minutes for Leicester to get a shot on target and a frustrating afternoon was made worse as Belgium midfielder Youri Tielemans’ struck a penalty against the post after Patson Daka was fouled inside the box.
Second-half substitute Iheanacho unlocked Walsall when his effort from the edge of the box deflected off the back of home defender Brandon Comley, turning it into a curling, dipping ball that proved too much for goalkeeper Owen Evans to handle.
With Foxes boss Brendan Rodgers saying after the match that first-choice striker Jamie Vardy will be out for “a few weeks” after suffering a gluteal injury in training, Iheanacho, who has started once in the league this sesaon, could get his chance.
“He will get more game time with Vards out for a few weeks. It depends on the type of game we are looking to play,” Rodgers told reporters.
“He has been first class, trains virtually every day and is very rarely injured. He sometimes starts games not so good, sometimes he is a little hit and miss, but you know when he plays to a high level he is a threat.”
Leeds reached the fifth round for the first time since 2016 as they avoided a slip-up at third-tier Accrington.
Jack Harrison put Leeds ahead with a spectacular long-range strike after 23 minutes before Junior Firpo and Luis Sinisterra scored within two minutes of each other midway through the second half to put Jesse Marsch’s men on course for victory.
Leslie Adekoya, 18, pulled one back for Accrington in the 81st with his first senior goal seconds after coming on, but it proved to be nothing more than a consolation strike.
Later on Saturday, Manchester United host Reading and and Tottenham Hotspur play at Preston North End.
