The Reds won their fourth game in a row as goals from Jimmy Smith, Karlan Ahearne-Grant and Enzio Boldewijn saw off struggling Grimsby.
Kewell acknowledged that the visitors posed a threat, particularly in the first half, but was full of admiration for his ‘solid’ defence.
He said: “Grimsby came here and had a game plan. They had some moments but we defended solidly today.
“I didn’t think they had any clear chances, only half chances and it was important to keep a clean sheet. If you keep a clean sheet, you always have a great chance to win games.
“Every team in football always strives to keep clean sheets. You always start from the back.
“It’s not only the back four, it’s the whole unit that defends and we were put under pressure, especially in the first half, but the quality in the end came through.
“Overall I felt we were strong defensively and we were confident. We are not afraid to play and even though the pitch wasn’t great, we were confident we could keep the ball.
“The conditions today changed the way we ultimately wanted to play but we did that in the right way.”
Kewell also credited moments of quality, particularly praising Enzio Boldewijn and Karlan Ahearne-Grant, who marked his home debut with his second goal in as many games.
He added: “Overall, it wasn’t the greatest of games but there were moments where we played extremely well.
“Even for the penalty, the movement that Enzio (Boldewijn) did was brilliant and Josh Doherty’s ball was also brilliant.
“It showed in Karlan’s (Ahearne-Grant) goal that he has no fear. To be able to drive at people, cut inside and finish is quality.
“Then it was good pass and move for the third goal. The ball Randall played for Enzio was exceptional and what a finish it was.
“Moments obviously win games but you don’t get Karlan’s goal without the first goal, and you don’t get the first goal without defending properly in the first half.
“It was a beautiful goal and we all enjoyed it, but so was Enzio’s movement for the penalty.
“I was a left winger and to see him do that is gold and to finish the way he did as well was fantastic.”