Newest starlet the major positive for Wigan Athletic boss
Latics saw their winless sequence extend to 11 matches at the DW, with goals from Matty Taylor and James Henry securing the points in a bottom-of-the-table encounter.
In truth, Latics should have been put to bed well before the 89th minute, when Norway Under-16 international Aasgaard - off the bench - popped up with a fine header from Tom Pearce's cross to ensure a nervy seven minutes of stoppage-time.
And head of academy Rioch - stepping into the management breach with Leam Richardson unavailable for family reasons - was understandably a proud man in assessing the latest product of the junior set-up.
"I'm obviously hurting with the result," acknowledged Rioch. "But there were so many positives from it.
"You look at someone like Thelo...who two years ago was about 5'2 in height.
"He wouldn't have been able to reach a cross like that two years ago, but it just shows when you wait for young, talented players to develop, you get your rewards.
"It was a great goal from him, and it gave us a big lift to take into the final stages of the game."
Unfortunately, the goal counted for nothing, with Latics once again paying the price for not making the opposition work hard enough for their goals.
"We know the manner of the goals we've been conceding, and they always look a lot worse when you're in the area of the table we are," recognised Rioch.
"Hopefully the more we work together on that, the better things will get, and the more we can start to eradicate things like that.
"We knew we were coming up against a very good Oxford United side.
"Karl Robinson's a very experienced manager and his teams are always well organised.
"We knew they'd be looking for a reaction after their defeat at Crewe in midweek.
"We knew we'd have to meet fire with fire, and what we asked of the players was huge commitment and being aggressive.
"I felt we got that in abundance today, despite the result.
"Even after their second goal went in, the reaction from the players was terrific.
"To keep going, and not let their heads drop, is not always easy to do in the current situation.
"We totally deserved the goal at the end, and we need to use that as a positive and try and just develop our game a little bit more while in possession."
Rioch also explained Richardson's absence from the technical area.
"Leam's just been dealing with a family issue, and we have spoken over the last couple of days," he added.
"He took the sessions in the early part of the week while I was working with the Under-23s, and I took over Thursday and Friday."