The Leicester lock was an early second half replacement for the injured Tom Rees. But Kay, winning his 54th cap for England, insisted the way his side allowed Wales to rally from a 19-6 deficit to record their first win at Twickenham since 1988 was the worst of his international reign.
Kay said: “Our intensity dropped in the first twenty minutes of the second half and we allowed Wales to get back into the game.
“We made some silly basic errors and they punished us. We compounded things ourselves and ended up on the back foot. That was probably the most damaging 40 minutes in my career.
“The first forty minutes were good and at the start of the second half we felt in great shape. We knew it was important that we built on that but we didn’t.
“We should have taken our chances in the first half and had more points on the scoreboard but we failed to do so. We weren’t complacent but we had lost sight of how we should be playing. It cost us.
“When you are winning 16-6 at half time and then kick another penalty early in the second half, you shouldn’t lose the match. And it’s all come down to errors on the pitch. We can’t use the injuries as an excuse but we must now make sure this never happens again.
“We weren’t surprised by the way they came back at us. The Welsh are a very proud nation and even when they go behind, they are never a beaten side. We knew they were a good side and had the ability and confidence to cause us problems. They deserved their win but we gave them the opportunities and boosted their game.”
“We can’t dwell on all the bad points that cost us because we played some good rugby in the first half and we must remember that we’re a good side. But it’s up to the players now. We must recover and bounce back against Italy next week.”
