Fulham's defense was bad last year. Historically bad. Was it the system? The coaching? Or the players? Moves like this seem to imply that the organization believes that they players simply weren't good enough.
If that's true, and you're going to be shopping for new center backs, you could do worse than Lewis Dunk. He was the best player on what was a pretty good defense. Brighton and Hove Albion only conceded 54 goals last year. That's less than Brentford, equal to Ipswich Town, and only four more than Watford. He's durable, having played over 100 times for Brighton including 44 times last season. He's young. Dunk is only 23 years old. He still probably has close to a decade of football in him and could be reasonably expected to improve over the next few years. So not only could he help you on the pitch, his value could grow allowing you to turn a profit on him in the future.
The article mentions a £2M bid. Frankly this seems low to me, and I'd be very willing for Fulham to spend more. Assuming that Fulham does get money back for Bryan Ruiz, Maarten Stekelenburg, and Kostas Mitroglou; they should have funds to spend without any new investment. Which is good, because there needs to be some more investment. But adding one good centerback could make a huge difference. Between Nikolay Bodurov, Shaun Hutchinson, and Dan Burn; you should be able to find one player to partner with him.
The hardest part of getting him might be fending of Premier League clubs. Everton, West Bromwich Albion, and West Ham United are all said to be interested in him. Everton fans are particularly keen on the idea. Fulham can't win a bidding war with those clubs, but none of them are likely to pay more than he's worth. If the £2M bid is correct, they're already doubling what Transfermarkt says he's worth.
I'll leave you with this. Isn't this the description of a player you'd like to have?