From Lemina's perspective, it is his best chance of securing another lucrative contract. Play well, make himself 'undroppable' and help keep them up and he gets a contract at Fulham. Even if they offered him a 3 year contract then it would be 2 years more on PL-level money than he'll get at Saints. Blow it and he'll go out on loan somewhere in Europe for the final year of his contract with Saints and after that he'll have to take the best that's on offer wherever he can - but it is very unlikely to be PL-level money. He clearly has no future at Saints - Ralph at least tried to re-integrate the skills Boufal has to offer into the squad, but Lemina has not been considered. I assume that Saints wouldn't be able to overturn the 'obligation to buy' even if Lemina did have a storming season with Fulham.