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  The Reds drew 2-2 at the Stadium of Light, less than 44 hours after beating title rivals Manchester City.
  "I told the players if nobody wanted to play I would never speak about it and not tell anyone, but nobody came. That was a good thing," said Klopp.
  Match of the Day pundit Martin Keown said: "Klopp looked tired himself."
  The draw left Liverpool five points behind leaders Chelsea, who visit Tottenham on Wednesday (20:00 GMT).
  Former Arsenal defender Keown said: "The high-intensity game has taken it out of them but it has been a good half of the season for them."
  Klopp said he "does not know exactly what I saw" during the draw at the Stadium of Light.
  Daniel Sturridge and Sadio Mane twice put the Reds ahead, but two Jermain Defoe penalties pegged them back.
  "I'm not able to explain it," said Klopp. "We can play better football but I'm not sure if you can play better with that break."
  Klopp made just one change to his starting XI, with forward Sturridge coming in for injured midfielder Jordan Henderson in an altered formation.
  Liverpool covered a total of 118.63km as a team, outrunning Sunderland, who clocked up 115.89km.
  That is in keeping with their performances over the rest of the festive period, during which they ran 116.87km in beating Manchester City and 118.94km in their 4-1 win over Stoke on 27 December.
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  Sunderland manager David Moyes suggested Klopp would have been widely praised had he been responsible for the home side's tactics.
  Klopp described the Black Cats as "the most defensive team I ever saw" after his side won the reverse fixture at Anfield 2-0 in November.
  "Maybe if I was a German manager, you might praise that, actually," said Moyes.
  "If I had been German, you might have been saying, 'great, you're doing something different'."
  England striker Sturridge was forced off 10 minutes from full-time on his first Premier League start since October.
  However, Klopp is hopeful the 27-year-old, who has scored six goals in 14 club appearances this season, will be back sooner rather than later.
  "He got a knock on his right ankle. I don't think it's too bad," said Klopp.
  Sturridge has had a series of injuries since signing from Chelsea in January 2013, including hip and thigh problems.
target: Liverpool manager Jurgen Klopp says he gave his players the chance to opt out of Monday's match at Sunderland if they were too tired - but nobody wanted to.