The pair - both 20 years old - were second-half substitutes as the Magpies faced Wolves in the Premier League Asia Trophy in China back in July. Watts replaced Ciaran Clark in the 59th minute in the pre-season friendly in Nanjing, while Allan replaced Jacob Murphy four minutes later in what was a first senior appearance for both of the young Academy products.
United lost 4-0 on a day when the likes of Owen Bailey, Elias Sørensen and Matty Longstaff also made their first appearances for the Magpies but, like Longstaff, Watts and Allan have kicked on from the experience and now find themselves within touching distance of their Premier League debuts.
Allan, who played for Cramlington Juniors before joining United in 2012, is the under-23s' leading goalscorer so far this term, having netted nine times in the first half of the season, and was an unused substitute in last weekend's Emirates FA Cup tie at Rochdale.
He signed his first professional deal in the summer of 2018 and, having spent much of his fledgling career as a winger until recently, has excelled as a forward this season, with his pace, workrate and finishing ability catching the eye.
"Going into this season, I had a chat with a few of the coaches and it was a big goal to try and score more goals," he told nufc.co.uk last month. "That's going well at the minute and I just need to keep doing what I'm doing to help the team.
Tom Allan in action against Wolves at the Nanjing Olympic Sports Centre
"For me, playing up front is not something that I'm not used to. I played there for a number of years and then when I worked with Ben (Dawson), he moved me out wide. I'm enjoying playing every game. That's all I've got to keep doing and try my best and see what happens from there."
Following on from his appearance on the bench at the Crown Oil Arena last weekend, Allan has continued to train with the first team this week.
England under-19 international Watts, meanwhile, was an ever-present for United's second-string last season but spent the first half of the current campaign on loan with League Two Stevenage, where he made 20 appearances in all competitions.
While the Boro struggled, Watts' displays stood out before he suffered a knee injury while playing in an FA Cup tie against Peterborough in November. Having recovered from that - and spent part of his rehabilitation training with Newcastle's senior squad - he was recalled on Friday morning.
The former Ponteland High School pupil has been named on the bench in the Premier League once before, at Fulham on the final day of last season, and, having agreed his first professional deal in 2018, signed a new three-year contract with his boyhood club earlier this term.
"To sign another professional contract for three years, I'm over the moon," he told nufc.co.uk at the time. "But I know those years in football can go quick, so I think I've got to take every game, every training session, every day as it comes, not look too much into the future, and just give what I've got day by day."
A versatile performer, the Alnwick-born ace has played up front and in midfield during his formative years - he scored an FA Youth Cup hat-trick against Brighton & Hove Albion in December 2017 and another treble for United's under-23s in a Northumberland Senior Cup quarter-final win against Blyth Spartans last season - but has played most of his football over the last two seasons at centre-back.
"I think I'm just one of those lads where if the manager wants me to play in a position, I just play it," he told nufc.co.uk in November. "I've played everywhere down the middle, I've got a good understanding of all positions, but obviously playing centre half now, for over a year without changing, has been good and brought opportunities like representing my country as a centre half and going away withe the first team as a centre half.
"So I'm just trying to grab my opportunities playing there. But in the future, if a manager wanted me to step in and play in midfield, I've got no problem with doing that and I'd give 100 per cent.
Kell Watts challenges Wolves' Niall Ennis in China
"Playing through the thirds, I know what passes the midfielders want, the number ten wants - he wants it in between the lines, he wants it on the half turn, punched in so he's got more time on the ball - so I think it's really helped playing higher up the pitch. Now I know what the strikers are wanting to do, whether they're going to fake-shot, because I've been in that situation myself where I'm trying to sell the defender. So I think starting higher up the pitch has massively helped me playing as a centre half, because playing as a ten growing up, being comfortable on the ball, is helping at the back. And obviously being a left-footer as well, there's not many left-footed centre halves, so it's another advantage.
"But I think most of the characteristics of being a centre half, I think I can work on my game, keep getting better, and I've got some of the attributes you need, so I'm happy playing there."
Watts made his international debut against Turkey during a European Under-19 Championship game in July 2018 - he has won two caps at that level - and, whether it comes at Molineux this weekend or not, one suspects his Premier League bow may not be too far away.
