The Senegal international has scored 11 goals in 18 appearances for the Turkish giants this season.
But the 29-year-old is potentially available on loan – with an option to buy – if Albion survive in the Premier League this season.
Diagne is understood to be on a shortlist of players along with a handful of other strikers currently playing in Europe.
And boss Sam Allardyce has vowed to leave no stone unturned this month as he searches for the men to boost Albion’s survival fight.
The Baggies boss claimed his first win since taking charge with a derby victory over Wolves on Saturday. But he still feels Albion need to make three more additions this month – with the boss revealing he is likely to run the rule over 250 potential targets. “I’m very adept in this window,” Allardyce said.
“It’s very difficult, but I’m used to doing business in it.
“So we’ll do between 100-150 – maybe even 250 enquiries during January to get the men we need. That was the same at all the other clubs I’ve been at.
“Hopefully, by the end of that we’ll get three or four good players who can go straight into the first team – or certainly not take very long before they do because we need that boost.
“We got a boost on Saturday. We need to carry on in the next three games before the end of January, and hopefully by then the players coming in will go on the pitch thinking: ‘We can win this game’.”
Allardyce has already signed Robert Snodgrass and Andy Lonergan this month. Snodgrass enjoyed an impressive debut in the win at Molineux, which was just Albion’s second in the Premier League this season.
The Baggies, who remain five points from safety, visit the Scotland international’s former team West Ham tomorrow.
Allardyce said: “It will be a great help to the players to get another good result, maybe even a win.
“If I add some quality players, the rest of the players here will look around and say ‘yeah, we can do better, because we’ve got better players here now’.
“That’s happened wherever I’ve been, whenever I’ve taken over a club in this position.”