Burnley manager Sean Dyche estimates he has made 500 phone calls this summer as he bids to assemble a squad capable of staying in the Premier League.
Dyche, 43, led Burnley to promotion from the Championship in May despite the Clarets having one of the smaller squads in the second tier.
He said: "We need more strength in depth but that doesn't just come with anyone. We keep looking and searching."
Burnley hope to add to their six summer signings before the end of the month.
Burnley have also been linked with Nottingham Forest midfielder Henri Lansbury.
Dyche added: "We work hard. I reckon I've made 500 phone calls over the summer to managers to agents to coaches, background on players etc. And that's just me, that's not counting my staff, the recruitment side of things.
"There's not a definitive number. I doubt we'll hit 25 senior players, but we definitely want to enhance the numbers."
Burnley begin their campaign by welcoming Chelsea to Turf Moor on 18 August.