Luke Hatfield spoke with French football expert Jeremy Smith, to get a better look at the striker.
Here's what he had to say.
What kind of footballer is M'Baye Niang, where does he tend to do best on the pitch?
Niang is a tall, strong attacker who is quite mobile and can play across the front line, but probably does his best work as a centre forward.
What would you say are his biggest strengths and weaknesses?
He's strong, he's quick and he is skillful.
Not the most natural of finishers but does have a good line in spectacular goals.
Probably his weakness is less ability but more mental - can go missing, doesn't always seem totally interested and has hints of bad attitude.
Niang has obviously caused some controversy off the pitch, what do you understand of his character?
There have been incidents in the past - part of the group of France U21 players (which included Griezmann) who received a ban for going clubbing between two important matches; high profile high-speed car crash while at AC Milan.
He seems to have matured a lot in the last couple of years, although always with a hint of tension between he and Rennes coach Julien Stephan, which goes as recently as last month as his not turning up for training before a friendly vs Benfica, all amidst rumours that he wants to leave.
Would he suit Premier League football in your opinion, and why?
I think he definitely fits the profile of a striker who can do well in the Premier League.
He has all the attributes that you would expect - tall and strong so able to deal with the physical side, good in the air, can play facing goal or with his back to it.
He just needs to be a little more clinical and learn to keep up a 100% attitude throughout matches.
West Brom have only just earned promotion back to the top flight, do you think Niang is the player to help fire in the goals to keep a club out of relegation trouble?
He has reached double-figures in the league for the last two seasons, for the first time in his career, and at 25 should now be hitting his peak.
A period of adjustment might be needed but, if he can keep his head straight, he should be capable of scoring 8-12 goals, which could be crucial.
Who would he compare to on the Premier League or world stage in your opinion?
My first thought was Victor Osimhen, who has just moved from Lille to Napoli, although Osimhen is better in all areas.
In the Premier League, I can see some similarities with Alex Lacazette in terms of mobility across the line and the skills to create and finish.
Niang arguably has more raw ability than Lacazette, but has not (yet?) come close to achieving the same success as he does not have the same work ethic and attitude.
Reports suggest that any deal for Niang would be a loan for Albion - do you think this is a deal that could work for all parties involved?
Rennes have brought in Guirassy, which suggests that they are already working on the basis that Niang could well leave.
I would have thought that they would prefer to sell, as they are still looking to expand their squad with a Champions League campaign as well as Ligue 1 this season.
But possibly a loan with a compulsory purchase option might be enough for them.