The two youngsters were part of Billy Stark's Under-21 squad who enjoyed a six-day training camp in Marbella.
Bragging rights will ride on the outcome of the game, but Watt is hoping that Celtic do not just come out as winners but that he gets a chance of some game time.
"Kenny and I were joking about it. On Saturday we'll be back to business and hopefully he won't be happy about it," he smiled.
"I just hope I'm in the squad and that I can get a chance if the gaffer needs me. I feel good after a bit of time in the sun and some training last week in Spain.
"It gave me the chance to get a bit of sharpness back because obviously I'm not playing 90 minutes every week and I really enjoyed it."
Celtic would be forgiven if they had an eye of Tuesday night's Champions League tie in Barcelona.
However, Watt is realistic enough to accept that simply being involved in the travelling party will be a bonus in itself.
"If I'm travelling with the squad, I'm happy with that," he said. "Even going over and watching a team like that will be unreal, different class.
"We will be prepared for Barcelona as much as we can, but the main focus is St Mirren.
"The Barcelona game is not in view just now, it's St Mirren.
"You need to do well in the league to be in the Champions League. We need to beat them and then focus on Barca.
"There's no point in losing games in the SPL and winning in the Champions League. You need to get a balance. Hopefully we can do well in both."
A victory over Saints would maintain Celtic's cushion at the top of the SPL table and allow them to go into their European adventure over in Spain in a confident frame of mind.
In the Champions League, they are two points behind Barcelona in Group G after beating Spartak Moscow in Russia last time out and recording a hard-fought draw with Benfica at Parkhead.
Watt knows the two matches against the Spaniards could go a long way to deciding if his side can progress from the group stages. However, it is fair to say that few would expect Celtic to come out of the game against Barca unscathed, despite the the La Liga side having a host of injury problems, including long-term absentee Carles Puyol.
"The next two games against Barca will be important," said Watt.
"Hopefully we can take something out of that and the game after that (at Benfica) will be the big one for us."