Jan Vennegoor of Hesselink believes that Celtic have to refine their scouting plans.
Gordon Strachan paid PSV Eindhoven £3.4m for the striker in 2006 but after three injury interrupted years he left the club on a free transfer to join Hull City.
Buying low and selling high is the motivation across the club these days highlighted by the deals involving Virgil van Dijk and Victor Wanyama.
Celtic’s scouting intelligence has expanded greatly since those days with Vennegoor of Hesselink now working in that area for PSV Eindhoven.
Dutch clubs are prolific at locating and recruiting young talent before selling them on to richer leagues- a system that their former striker believes Celtic have to develop further.
“One of the things that Celtic should do is think longer term about who they will bring in if they sell players,” Vennegoor of Hesselink told The Sun.
“That’s the philosophy that can make the difference — and help them reach last 16.
“If you have a plan on how you replace Dembele, for example, and even beyond that.
“We have just made a deal for PSV for Hirving Lozano from Mexico — and that’s something we have been working on for two years.
“So sometimes you have to think a little bit differently and look to the future.
“You need to plan. If you sell a really big player for £30m, let’s try to get three players of £2-3m and they can grow, achieve their potential and then they can help your club progress in the Champions League and then be sold on.”
Brendan Rodgers has switched Celtic’s scouting focus more towards England as he taps into his know how of that market.
A deal to sign Olivier Ntcham from Manchester City is expected to be completed this week with last season’s most significant signings, Moussa Dembele and Scott Sinclair coming in from Fulham and Aston Villa.