After a goalless first half in the Welsh capital, Dutch midfielder Wijnaldum broke the deadlock in emphatic fashion 10 minutes into the second period, striking a crisp half-volley from Trent Alexander-Arnold’s corner.
Liverpool rode their luck in the second half as Alisson’s costly error almost gifted relegation-threatened Cardiff the equalizer, but Sean Morrison failed to convert.
Milner then secured the three points nine minutes from time, converting from the penalty spot after Morrison had clumsily hauled Mo Salah to the ground.
Just 24 hours earlier, Liverpool had seen Manchester City regain the lead at the top of the Premier League thanks to a hard-fought victory over Tottenham and knew only a win against Cardiff would keep them in the hunt for a first top flight title since 1990.
Liverpool now sit two points clear at the summit with City’s game in hand against Manchester United to come on Wednesday.
Though the bitterest of rivals they may be, you get the sense Liverpool fans will be cheering on United in three days’ time.
Victory takes Liverpool onto 88 points, a new Premier League record for the club and a total that would have been good enough to win the league in six of the last 11 seasons.
Manchester United humiliated
Manchester United suffered the worst defeat of Ole Gunnar Solskjær’s reign as manager, going down 4-0 against Everton at Goodison Park.
The hosts took a commanding first-half lead thanks to goals from Richarlison and Gylfi Sigurdsson, before Lucas Digne and Theo Walcott turned the game into a rout in the second half.
So poor was the performance — United didn’t register a shot on target until the 85th minute — Solskjær went over to the traveling fans after the match and held his hands up in apology.
United have now conceded 48 goals this season, their worst defensive tally in Premier League history — and there are still four matches left to play.
“From the first whistle, everything went wrong,” Solskjaer told Sky Sports after the match.
“I just want to apologize to the fans. They’re the only people with the badge on today who can hold their head high, because we can’t.”
Defeat leaves United two points behind Arsenal in fourth place — the final Champions League spot — though the Gunners play their game in hand against Crystal Palace later on Saturday.
The loss to Everton, which sees Solskjær’s side now on a run of six defeats in eight games, was the first time United have conceded four goals in a Premier League game since October 2016.
In the build up to this game, Solskjær had abruptly stated that some of his players needed a “reality check” following a poor run of form which culminated in last week’s humbling 3-0 defeat to Barcelona.
If he had been hoping for a reaction him team on Sunday then United’s performance will have left him exasperated, as Everton took a 2-0 lead with less than half an hour played.
The Norwegian coach, evidently bitterly disappointed with the performance, hauled off Phil Jones and Fred at half time for Ashley Young and Scott McTominay.
But things went from bad to worse for the visiting side as Digne made it 3-0 within 10 minutes of the restart and Walcott put the icing on the cake 10 minutes later.
Since that improbable comeback away at PSG in the Champions League — a ninth away win in a row — United have now lost five consecutive games away from home for the first time since 1981.
Up next is the small matter of the Manchester Derby, as Solskjær’s side welcome Pep Guardiola and Manchester City to Old Trafford on Wednesday in the hope of derailing their Premier League title charge.