The Foxes are likely looking at how the player can help them disrupt the opposition and launch counter-attacks. We saw against Manchester City how Leicester hopes to create from defence and the possessive role their defenders must have when dominating a match. Jannik Vestergaard has been critical in this, making more sideways and forward passes per 90 minutes than any other LCFC defender.
That role is important. Crucially, it does not require pace. The primary aspect of this role is to intercept, clear, make the right choices, and win the ball before passing it swfitly onwards. Compared to his peers in the Top 5 Leagues of Europe, this young defender is amongst the elite in interceptions and clearances. Further, we can see the player wins a great many of the ground duels they partake in and almost all their aerial battles thanks to his height and physical strength.
That elite duelling mentality is better served by a player such as Khusanov who also reads the game exceptionally well. They like to take up certain vacant spaces or man-mark the right person at the right time. This can leave him exposed should the marked player peel away as a dummy, but usually as a slower CB the player does not go chasing geese. They are well-focused, understand the game well, and usually make the right choices.