Steve McClaren felt Aleksandar Mitrovic's showing was one of few bright spots to come out of Newcastle United's 2-1 defeat to York City.
The 20-year-old Serbia international made his debut on Wednesday - a week after signing from Anderlecht - having not trained in 10 days but showed glimpses of quality as the League Two side sprung a surprise.
Shortly after Mitrovic's departure 20 minutes from time, Ayoze Perez scored Newcastle's only goal but McClaren hailed his new signing's display.
"He showed what potential he has," the former Derby County boss explained.
"He hasn't trained for 10 days so missed half a yard. But he made great runs and has that bit of devil about him, a very good signing."
McClaren's men finish up pre-season against Borussia Monchengladbach on Saturday before beginning their Premier League campaign against Southampton.
Having been appointed John Carver's replacement in June, McClaren acknowledged a hint of frustration at how Newcastle's close-season preparations are going.
"I'm like every manager in pre-season, you always have concerns because you never quite know where you're at," he added.
"Especially when you just come in and you're trying to establish a look, play catch-up and get to know everyone.
"That's what I'm doing, we're learning a lot but with 10 or 11 days left, they'll be interesting days.
"I've had plenty of pre-seasons, good ones, bad ones, but you never know until the first game. It's been very short, we've been to the [United] States and come back, so we're just trying to catch our legs again.
"I'm pleased with the workouts we've had and pleased with the attitudes of the players, Saturday will give us a clearer indication of where we are but in the long term I'm very impressed by what we've got.
"We are where we are, you never know if you're on the right track until the season starts. Monchengladbach will be a good test and then we'll have the final week to polish things up."
