Replacing striker Matthew Simon midway through the second half of the 1-0 loss to Western United was a 19-year-old widely acclaimed as the next big thing in Australian soccer.

The previous day, the Mariners had agreed terms for the end-of-season transfer of Alou Kuol to VfB Stuttgart in the German Bundesliga which was reported to be for a six-figure fee high enough to secure the financial future of the embattled NSW franchise.

Born in the Sudanese capital Khartoum, Kuol moved to Australia aged four, grew up in Shepparton and has taken the A-League by storm, scoring seven goals across 17 appearances this season despite starting most games on the bench.

He earned the February nomination for the A-League's young player of the year after four games in which he either scored or assisted goals on average every 13 touches or 28 minutes.

Despite not scoring in Launceston, his involvement was reminiscent of Dante Exum playing for Victoria in the 2013 under-20 national championships at Elphin Sports Centre a year before becoming a round-one NBA draft pick.

Both coaches were glowing in their assessment of the teenage talent.

Mariners coach Alen Stajcic said: "We're really happy for him, we're proud of him. He's worked extremely hard in the couple of years he's been at our club.

"It's been an amazing ride for him from Shepparton to come on trial, get into the team and make his debut last year for the A-League team and have the breakout season that's he's had so far. It's fantastic for him and I wish him all the best.

"After this season, we'll obviously keep close tabs on him but we've got another nine games with him here where he's an important part of our club and we saw that where he definitely changed the game where he came on tonight as has been his role recently and was a constant threat I saw."

United coach Mark Rudan echoed the praise for Kuol whose late brace won the reverse fixture between the sides earlier in the season.

"He's a talent and well done to him, he could be the next big thing in Australian football," Rudan said.

"He's secured himself a contract overseas and congratulations to him and the Mariners. He killed us in the first round, we were 2-1 up, he came on, scored two goals and we lost that game. (But tonight) we nullified him. We knew he was going to come on at some point."