The Netherlands international was caught on camera congratulating the former West Ham United and Tottenham Hotspur striker during the Tyne-Wear derby.
Defoe broke the deadlock in the Premier League encounter at the Stadium of Light on the stroke of half time with a truly sensational volley.
As the players headed down the tunnel during half time, Krul was caught on camera congratulating Defoe for his wonderful strike.
The 27-year-old’s action is unlikely to have pleased the Newcastle fans, but he has now explained what he told the Sunderland star.
“What I actually told him I probably cannot repeat on television as it wasn’t nice,” Krul told Sky Sports. “It was a fantastic goal, everybody can accept that. What I told him was in the region of what a lucky guy he was..
“Listen, I have been here for 10 years, I am hurt as anybody else. Whoever wants to put a negative spin on that is not justified."
The 1-0 defeat at the Stadium of Light leaves Newcastle 13th in the Premier League table with 35 points from 31 matches, nine points above the relegation zone.
Newcastle are back in league action next Monday when they face Liverpool away from home at Anfield.