The summer transfer window is set to be a busy one for Brendan Rodgers and Celtic. The treble winners and current reigning Scottish Premier League champions are dominant domestically but it’s in Europe where showings and performances will have to improve.

Coupled with the fact vultures are circling the talented Kieran Tierney and the prolific Moussa Dembélé, it could be quite the revolving door at Parkhead over the summer months. The club will no doubt want to keep their best players but cashing in on one could provide them the funds to strengthen their entire squad.

With that in mind, we’ve taken a look at the top five Celtic rumours using our Football Whispers Index, which scores the validity of transfer rumours out of five, to see who could be joining the Rodgers revolution.

Ryan Kent – Liverpool – 1.6

Various outlets claim Rodgers is keen to raid his former club Liverpool to bring in attacking reinforcements. With Patrick Roberts set to return to Manchester City this summer they're in need of someone to play on the right side of the three-pronged attack.

Kent spent last season on loan at Barnsley and put in a number of eye-catching performances. The 20-year-old has been linked to Bournemouth, who reportedly had a £7million bid turned down for the winger.

However, the Celtic boss will hope his connections with the club will help him get a favourable deal. The lure of first-team football could well be enough to convince Kent to move up north for a season or two.

Martín Cáceres – Southampton – 1.5

Swansea target Martin Caceres is without a club at the moment.

The Uruguayan centre-back, who only joined Southampton in February, is already looking to move on after just making one Premier League start for the Saints.

The 30-year-old is a target for many clubs across Europe and would bring a wealth of experience to any squad he joined up with. Celtic are in the market for a centre-back, perhaps as a replacement for the 36-year-old Kolo Touré.

While the Bhoys might not be able to offer the former Juventus man as much money as others, they would be able to offer him first-team football. Albeit depending on the defenders fitness. He could be a shrewd signing.

Robin Olsen – FC Kobenhavn

Kieran Tierney | Celtic FC | FWTV by FootballWhispers

Swedish goalkeeper Olsen is on Celtic's radar as the club look to bring in a long-term no.1. With questions being asked of current incumbent Craig Gordon as well as back up Doris De Vries.

The 27-year-old, who is also a transfer target for Premier League new-boys Newcastle United, did nothing to put a stop to speculation recently when asked about his future.

Olsen told Sport Expressen in Denmark: “You never know what's going on in football. I have the ambition to start the next season with FCK, but you never know…”

Johan Djourou – Hamburg – 1.3

The former Arsenal man is said to be close to joining Ligue 1 side Montpellier, but until the ink is dry on his contract anything is possible.

Like with the interest in Cáceres, the interest in Djourou comes with Celtic keen on adding a defender with European experience to their squad.

The Swiss International, still only 30-years-old, has been tentatively linked with a number of clubs over recent weeks.

Though once highly-rated, his stock has fallen since his move to the Bundesliga. It's hard to impress while playing for a side regularly battling relegation.

However, there's still some talent there just waiting to be utilised and Rodgers may relish the opportunity. He's also out of contract at the end of June meaning he'd arrive in Scotland for nothing.

Oumar Niasse – Everton – 1.2

Everton's once-forgotten man is now being courted by a number of clubs after an impressive loan spell away at Marco Silva's Hull City. He didn't do enough to keep the Tigers in the Premier League but did more than enough to thrust his name back onto many lists of potential attacking targets for clubs this summer. There was a reason

With Everton keen on Dembélé, Niasse has been linked with going in the opposite direction.

The 27-year-old attacker, given a season in Scotland, could turn a quick profit for the club and act as a short-term solution to potentially losing the French hot-shot. Niasse scored four goals during his spell with Hull, including one against Liverpool.

Football Whispers, however, believe Dembélé should stay at Celtic for another season.