I saw 2 seasons of him, but yeah I might be judging at Super League level, may be he is OK for Championship level.
But I don't get where you get your data, Tetteh never scored 15 goals in a season during his career, his best is 11 goals in Czechia and 7 goals in Turkey. His two seasons total is 12. And if you think Turkish league as 6th best league, well man you are way off, we are out of top 10 last season and probably around 20s next year according UEFA coefficients unless a miracle happens this year. Huge economic crisis happening and all clubs are caught with 10 times more debt than their annual budget. Government started a program to save them and arranged cheap loans from state bank.
Estupinan scored 15 in 28 in the 6th best league, not Tetteh.
Tetteh looked strong when he came on at peterboro. Maybe he's been pumping in the gym all summer?