Virgil van Dijk said Netherlands were below their best against Belarus, despite a 2-1 win in Minsk to close in on Euro 2020 qualification.
Georginio Wijnaldum came to Netherlands' rescue as their strikers misfired in Minsk, with his double sinking Belarus.
Northern Ireland's goal came thanks to a Matthijs de Ligt error, but Ronald Koeman defended the centre-back ahead of facing Belarus.
Juventus team-mates Matthijs De Ligt and Cristiano Ronaldo have a special quality in common, according to Ajax chief Edwin van der Sar.
Netherlands moved top of Group C with a comeback win over Northern Ireland on Thursday but will be without Memphis Depay against Belarus.
Netherlands scored three late goals to overcome Northern Ireland, whose tactics left Ronald Koeman unimpressed.
Northern Ireland led with 10 minutes to go in Rotterdam, but three late goals moved Netherlands top of their Euro 2020 qualifying group.
Northern Ireland led in Rotterdam through Josh Magennis' goal, but Memphis Depay scored a brace either side of Luuk de Jong's goal.
Netherlands can go joint-top of Euro 2020 qualifying Group C by beating Northern Ireland, but Ronald Koeman foresees a tough contest.
Matthijs de Ligt is still learning from the "Italian school" of defending at Juventus, according to Ronald Koeman.