Widdop, 24, made his first start of the tournament in the Wembley showdown, which saw the defending champions win 20-18 due to Shaun Johnson‘s last-second try.
“We played really well and we did deserve to get the win,” said Widdop.
“But in these big games you can’t switch off, and in that last set we let them over the try line.”
The former Melbourne half linked well with fellow playmaker Kevin Sinfield – a partnership that has hardly played together before.
“I haven’t played much footy over the past few weeks but I was happy with how I played and how the team played today.
“There’s nothing more to say really, we’re gutted but there’s not much we can do. We just have to make sure we work towards getting the win next time round.”