Newcastle manager Eddie Howe conceded injuries and a heavy schedule have taken a toll on his side after losing 2-0 on his return to Bournemouth on Saturday.
Dominic Solanke struck twice in 13 second-half minutes to lift the Cherries out of the relegation zone.
Newcastle started without a recognised striker and handed a first Premier League start to teenager Lewis Miley with Howe's squad stretched to the limits.
Callum Wilson, Alexander Isak, Harvey Barnes, Dan Burn, Jacob Murphy, Sven Botman and Matt Targett were all sidelined by injury, while Bruno Guimaraes was suspended. Sandro Tonali is serving a 10-month ban for breaching betting rules.
The Magpies are in the midst of their first Champions League campaign for 20 years and have also progressed to the quarter-finals of the League Cup.
"It was just a game too far and we couldn't respond. Bournemouth played well but we were well below par," said Howe, who managed Bournemouth for 11 years in two spells between 2008 and 2020.
"It was a tough afternoon. We weren't ourselves in possession or out of possession. If you can't do that at this level, it will be a difficult day.
"When we are under fatigue and stretched, we usually respond better. We need to dust ourselves down and come back in strong."
There could be further bad news for Howe as Miguel Almiron had to be replaced after just 31 minutes with a hamstring injury.
"We have a whole host of players and we need them back as soon as we can," added Howe.
"We have a busy December as well so it's not a good mix but something we have to get used to."
Victory was just Bournemouth's second in the Premier League under Andoni Iraola.
Solanke smashed past Nick Pope at his near post when the ball broke his way inside the box on the hour mark.
The former Liverpool striker then bundled home from close range after Newcastle failed to clear a corner.
A second win in three outings takes Iraola's men three points clear of the bottom three.
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