Benitez told Sky Sports News after the game: "It was a great effort against a good team.
"To go to the point where it was 0-0 and with the chances that we had with a couple of counter-attacks I would say again against a good team, it was a pity that everything changed. Things weren't going well with the injuries but after the sending-off it changed everything.
"What I would say is that [Shelvey] made a mistake. Still I would like to see if it's more dangerous this situation or the tackle from behind (Kane on Florian Lejeune). But it's no excuses. He made a mistake and that's it. He knows he's made a mistake and he's apologised but it can't change anything now."
Up next for Newcastle is a Premier League meeting with fellow newly-promoted side Huddersfield Town at the John Smith's Stadium in next Saturday's early kickoff.