Liverpool put the pressure back on Manchester City in the title race after taking over top spot again on Sunday.
The result lifts Liverpool two points ahead of their rivals, though City do still have a game in hand going into the closing weeks of the campaign.
Pep Guardiola's side can leapfrog over the leaders with victory against Manchester United at Old Trafford on Wednesday, though Milner admitted Liverpool are at least making it tougher for the reigning champions to retain their crown.
"All we can do is keep the pressure on them and win our games," the former City midfielder told Sky Sports.
"It makes it tougher for them, as if we slip up it gives them that little cushion, allows them a draw or a slip-up.
"All we can do is win the rest of our games and hopefully that's good enough. If not, fair play to City, but we are asking all the questions of them that we can.
"Both teams have been ruthless and clinical in doing their jobs. It's not easy week on week - we've lost one game all year and were second [before Sunday's result]. We go back top now, though, and puts a bit of pressure on them.
"We just have to concentrate on being perfect and will see if that's good enough."
Wijnaldum's opener - a well-struck shot from a set-piece routine - was crucial against Cardiff, with the home side having made life tough for their opponents.
Yet despite having to wait until the 57th minute to break the deadlock, the Netherlands international was always confident Liverpool would win after controlling the first half.
"It's always a relief, especially at this time of the season. You know that you have to win - in the first half we created chances but didn't score," Wijnaldum said in his post-match interview.
"Everyone was waiting for a goal and when you get it, it's a relief. I was really happy, and the fans were really happy, too."