The Latics squad is set for an overhaul following relegation from the Premier League, as well as former manager Roberto Matinez's departure from the club.
With the likes of Maynor Figueroa and Franco Di Santo having already left the club and speculation linking players such as Arouna Kone away, Coyle knows he needs to strengthen for the campaign ahead.
He has also challenged players like 20-year-old Fraser Fyvie, who made eight league and cup appearances last term following his purchase from Aberdeen, to step up.
He told the Wigan Evening Post: "There's no doubt that we need a minimum of six players, just to replace the players who have already left.
"We also have one or two younger players coming through who will supplement the squad, players like Fraser Fyvie, and they will get their opportunity to show what they can do in pre-season."