England winger Townsend, who joined from Tottenham Hotspur in the January transfer window, has a hamstring problem.
"We're assessing him," McClaren told a news conference on Friday. "We don't want to risk him because it's a hamstring and he needs his speed."
However, second-bottom Newcastle will have midfield pair Siem de Jong and Vurnon Anita back in the squad.
McClaren's men lost their sixth successive Premier League away game on Wednesday, going down 1-0 at Stoke City, and McClaren said it was now up to the players to give worried home fans a lift.
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"We've lost one in our last six at home, we've given the crowd something to cheer about and we need to do that again," he said.
"We don't want anything to destabilise what we are trying to achieve between now and the end of the season."
Sixth-bottom Bournemouth, experiencing their first season of top-flight football, eased relegation fears with a 2-0 win over south coast rivals Southampton on Tuesday and McClaren was full of praise for their young manager Eddie Howe.
"I admire what Eddie has done there," said the Newcastle boss. "They always had a great chance of staying up.
"This is a very difficult game for us."
(Writing by Tony Jimenez; Editing by Ed Osmond)
