Newcastle manager Alan Pardew says the Magpies may have to change their style of play following the sale of midfielder Yohan Cabaye.
With top-scorer Loic Remy suspended, United were beaten 3-0 by Sunderland on Saturday, the fifth time in six league games they have failed to score.
"We have lost a good player and have another who scores goals sitting out," said Pardew.
"A lot of the play went through Yohan, so maybe we have to change our style."
A third successive derby defeat came at the end of a week in which Newcastle sold Cabaye to Paris St-Germain for £19m, failed to sign Lyon midfielder Clement Grenier, but did acquire Dutch striker Luuk de Jong on loan.
The 3-0 reverse against the Black Cats matched the result from the same fixture last season, and also extended the Magpies' run to only one win in seven games.
"The better team won, for sure," added Pardew. "We didn't look our usual selves. Maybe we were too hyped up for it.
"We gave the ball away and we struggled. Though we created chances, we didn't look like we had the conviction to score."
Newcastle lost 2-1 at the Stadium of Light in October, but won seven of their next nine Premier League games and, despite their poor form, are still eighth in the table.
"We have lost two of our big goalscoring options and were also without Fabricio Coloccini. They are massive players for us.
"We have to find another way to play, maybe a with a back-to-basics element to make sure the second half of the season mirrors the success of the first half."
Pardew was confronted by a fan midway through the second half at St James' Park, while his side were booed at both half-time and the full-time whistle.
"You don't want to lose 3-0 at home to your rivals and we have done it two years in a row," continued Pardew.
"We have to take stock of today because we know how important it is to the fans, but that won't wipe away the memory.
"We have to get ready for a tough game at Chelsea next week with a game plan that will work."