The Reds boss believes the "ordeal" of making an Anfield debut played a part in his side's 1-1 draw against the Black Cats and feels Richardson should have seen red early on
Kenny Dalglish believes that nerves may have affected Liverpool's new signings in their 1-1 draw with Sunderland on the opening day of the season.
Four summer signings - Jose Enrique, Jordan Henderson, Charlie Adam and Stewart Downing - made their Liverpool debuts at Anfield on Saturday.
On a frustrating afternoon for Dalglish's side, the Liverpool players appeared to tire in the second-half and the Scot believes that the players may have felt drained because of the occasion.
He said: "The four boys who came in would have had nerves. It's a big ordeal coming out to play your first game at Anfield, especially for Jose Enrique who only signed yesterday.
"I thought they all did something in the game that you will remember them for. We are happy with them and they will improve.
"I think the players were a little bit nervous. Like I said, it's a big deal making your debut at Anfield."
Liverpool took the lead in the 12th minute through Luis Suarez's glancing header but were pegged back by a fierce volley from Sebastian Larsson 12 minutes after the restart.
But Dalglish felt the key moment of the game was the award of a sixth minute penalty for the hosts after Kieran Richardson brought down Luis Suarez in the box.
The Uruguayan subsequently missed the spot-kick but Bruce felt referee Phil Dowd should have shown Richardson a red card as Suarez was through on goal.
"I suppose nine-and-a-half out of 10 referees would have sent Kieran [Richardson] off," said Bruce.
"You don't want to see people sent off. I don't know what the rulebook says but it was a clear goalscoring opportunity. Luis Suarez was one-on-one with the goalkeeper - you can't get any clearer than that.
"I think over the game, for their effort and commitment, a draw was probably about right. They worked really hard."