The Reds striker headbutted Eagles defender Joachim Andersen during the second half of the Premier League clash. Nunez was shown a straight red card.
Westerveld was disappointed with the Uruguay international's actions on the night.
Speaking with BBC Radio 5 Live, he said the following about the incident: “People try to test him but this is not the way to retaliate. You can’t do anything worse than this.
“It was a frustrating night for him. He missed a couple of chances and probably should have scored one or two. First time at Anfield he probably expected a little bit more from himself, but this was just absolutely inexcusable.
“Hopefully it’s only three games but it’s not good timing as he is the only striker we have at the moment. It’s a pretty easy talk with him (for Jurgen Klopp) because he knows what he did with the reactions. He knows he was wrong.
“Like Jurgen says he will learn from it. It’s only the beginning of his career at Anfield and I think it will definitely not happen again.”
🗓 #OnThisDay in 2013, Simon Mignolet made his debut for the Reds.
🔴 204 appearances
👐 66 clean sheets
🏆 Champions League 2019
Anfield Watch Verdict
Westerveld is spot on. Nunez really let himself down. You've got to be wondering what is going through his mind to headbutt an opposition player.
Nunez is only human, so he is bound to make a mistake or two out on the football pitch. It was a frustrating night for the striker.
Nunez should have scored during the first half, but it wasn't meant to be. It would be fair to assume that the 23-year-old will be desperate to make an impression when he takes to the field again.
Nunez won't want to let his teammates down again.