Goga's having another great game so far in his second Euroleague appearance, with 13 points, 3 boards, and 2 blocks at halftime. There's little precedent for a teenage big contributing at a high level in Euroleague (other than Doncic, if you count him as a big). Off the top of my head...
-Valanciunas was 18 years old for his only Euroleague season, in which he averaged 7.7 points, 5.8 rebounds, and 0.7 blocks per game.
-Bargnani averaged 3.7 points, 2.1 rebounds, and 0.2 blocks per game in his age-19 season.
-Vesely averaged 8.4 points, 4.9 rebounds, and 0.5 blocks per game in his age-19 season.
Did I miss anyone?
EDIT: He finished with 23 points, 8 boards, and 2 blocks. The 23 points were a game high in a matchup that featured ex-NBA players Norris Cole, Earl Clark, Mike James, and Mindaugas Kuzminskas as well as Cavs prospect Arturas Gudaitis.
Through two games he's now averaging 20 points, 7.5 rebounds, and 3 blocks.
Update on this post...here are per-40 stats, to adjust for the fact that Goga's getting more playing time than these other guys. Also added Zizic and Saric, who were reasonably productive in Euroleague at a slightly older age.
Goga Bitadze (age 19): 24.1 points (67% true shooting), 11.0 rebounds, 1.6 assists, 0.8 steals, 5.3 blocks, 1.2 turnovers, 6.9 fouls
Jonas Valanciunas(age 18): 19.9 points (75% true shooting), 15.0 rebounds, 0.5 assists, 0.5 steals, 1.7 blocks, 3.6 turnovers, 7.9 fouls
Andrea Bargnani (age 19): 16.2 points (57% true shooting), 9.2 rebounds, 0.7 assists, 0.7 steals, 0.7 blocks, 1.8 turnovers, 6.3 fouls
Jan Vesely (age 19): 13.5 points (62% true shooting), 7.9 rebounds, 2.3 assists, 1.2 steals, 0.7 blocks, 2.3 turnovers, 6.8 fouls
Ante Zizic (age 20): 16.5 points (66% true shooting), 12.3 rebounds, 0.6 assists, 0.4 steals, 1.4 blocks, 2.3 turnovers, 3.6 fouls
Dario Saric (age 20): 16.2 points (53% true shooting), 10.4 rebounds, 3.8 assists, 1.2 steals, 0.7 blocks, 3.1 turnovers, 3.3 fouls
Based on this, Goga has really separated himself from the pack in two places.
First, he's been extremely prolific and efficient offensively. The volume, especially playing for a poor team, is not too surprising...but the fact that he's been scoring efficiently and not turning it over is impressive given his very large offensive role.
Second, he's been an absurdly prolific shot blocker. He's actually blocking shots at a higher rate than all of the other guys on this list combined. This is where it's especially important not to pigeonhole him as "just another Euro big"...he's a fantastic athlete for his size with a sky-high defensive ceiling.
If he keeps producing at or near his current level in those areas (and especially if he continues to make occasional threes), I'd have no problem taking him top-5.