The Newcastle boss saw his side fall to a 3-0 loss against Gus Poyet's men in the 149th Tyne-Wear derby, capping a miserable week in which midfielder Cabaye joined Ligue 1 champions Paris-Saint Germain.
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"It's been a tough week, there's no doubt about that," Pardew told reporters. "We lost Cabaye and no transfer comes in, so it's been a tough week.
"I think when you lose a player of Cabaye's class you want a replacement, it didn't arrive and I have to accept that and I have to get the best out of the group.
"We didn't have [Loic] Remy [who was suspended], that was a big loss. We created big chances but we lacked conviction and he doesn't lack that.
"It would have been nice to have a player to give me a boost for the second half of the season. The bottom line is the players have to find a game plan that's going to work for us."
Pardew added that he felt the first goal changed the complexion of the game, with Sunderland profiting from Vurnon Anita's clumsy challenge on Phil Bardsley.
He added: "There's disappointment in the result and the performance. The first goal was very, very important. They got it, after that we lacked composure."