Celtic head into this summer transfer window in as strong a position as they have been in for years and years. Off the back of an unbeaten domestic treble, all Brendan Rodgers needs to do is tweak the squad for them to be a massive force again next season in Scotland.

In Europe, it's tougher, although the progress shown by some of the squad over the last 6 months has been incredibly impressive and players like Stuart Armstrong or Callum McGregor have their chance to show what they can do on the biggest stage again.

Still, additions do need to be made and although the Hoops have significant resources by Scottish standards, their budget is dwarfed by most other teams in the UEFA Champions League.

That means they have to maximise said resources and pick up quality players on the cheap.

With that in mind we've compiled a list of three elite players who have been released by their clubs and who can really add something to the Hoops with their experience and ability...

Jesus Navas

Having come to the end of his contract at Manchester City, Navas is without a club, despite making 35 appearances for Pep Guardiola last season.

The right-sided player has been a regular at the Etihad over the last four seasons and leaves the club having made 183 appearances. With a stellar career at Sevilla also behind him, he has a quality and experience beyond most players at the Hoops.

Wages are of course an issue but Celtic can offer him regular football, which at the age of 31 may be welcome, and the chance to play in the UEFA Champions League.

Navas has made close to 90 appearances in UEFA competition down the years and that makes him very valuable to a club like Celtic who need experienced pros to help them progress in the group stages.

He also has a versatility to play from right-back to right-wing, making him cost effective too. The Hoops needs a replacement for Patrick Roberts and competition for Mikael Lustig and a move for Navas would kill two birds with one stone.

It would be ambitious but with the absence of a transfer fee, we don't see why they shouldn't at least enquire about his availability.

Martin Caceres

While he may have only made one appearance for Southampton since joining in January, central defender Martin Caceres has lots of experience at the top level of football having made over 100 appearances for Juventus in Serie A and over 100 appearances in Spanish football for Sevilla, Barcelona and Recreativo.

He's also gained 68 caps for his country, Uruguay, playing in two World Cups and multiple Copa Americas. It’s clear he has the experience that would greatly enhance the Hoops squad.

Brendan Rodgers is hoping to make significant progress in Europe and bringing in an experienced hand could in the backline be a big step towards that, especially when you consider he has dozens of appearances in UEFA competition.

We saw the influence of Kolo Toure on the Hoops' performances in Europe last season and while ultimately you can see his career coming to an end, at 30 years old Caceres still has plenty of seasons left in him.

Gael Clichy

Another Manchester City regular who is leaving the Etihad this summer is Gael Clichy. The 31-year-old made 37 appearances for City across last season but Pep Guardiola clearly wants to pursue other options on the left hand side of defence.

Like the others on his list, he offers an experience at the top level that could be a great asset to the Hoops next season. Kieran Tierney at 20 years old has progressed massively at Celtic but at times last season in Europe looked a little naive and off the pace, most notably against Barcelona.

Besides, bringing in a player of Clichy's calibre would only enhance Tierney's development as an elite left-back.

With a distinguished career with Arsenal and City behind him and having gained 20 caps for France, Clichy would likely be a star in Glasgow, giving Tierney the serious competition he needs and also perhaps even deputise on the left hand side of midfield in place of Scott Sinclair if need be.