Having returned from a fruitful tour of New Zealand earlier this week, manager Alan Pardew rested most of his senior players - though Cheick Tiote, given time off to recover from his World Cup exploits with Ivory Coast, was a notable inclusion.
Wednesday shaded a first half in which they struck the crossbar through Sam Hutchinson, but the Premier League outfit sealed victory after the interval thanks to new arrival Ayoze Perez.
It was the Championship side who fashioned the first chance, Chris Maguire clearing the crossbar from inside the box following strike partner Gary Madine's cushioned header.
Emmanuel Riviere, who scored on his Newcastle debut in a 4-0 win over Sydney last week, then saw his toe-poked effort drift just wide with 24 minutes gone.
Giles Coke and Atdhe Nuhiu both went close within a minute of each other, while Joe Mattock sent a powerful shot just wide of Rob Elliot's right-hand post.
The Newcastle goalkeeper was helpless to stop Hutchinson's 37th-minute strike flying past his outstretched right arm, but the ball bounced off the underside of the crossbar and was cleared to safety.
A steady stream of substitutions hampered the game's flow after the interval, with chances at a premium.
But when Perez, who joined from Tenerife in June, was picked out by Gabriel Obertan in the 66th minute, the 21-year-old provided a cool side-footed finish past Chris Kirkland.
Stuart Gray's men should have levelled 12 minutes from time, but the unmarked Franck Betra contrived to miss from 10 yards.
