There are some players who may seem to be catching up with age but still put in some impressive performances for their club.
While they may still be useful, it is time for these clubs to search for an able replacement to make sure the player doesn't suffer fatigue and the team is left with no proper back-up.
While some of these players are not performing at their best, others are still putting in a shift for their teams at the highest levels. Either way, they need to find replacements and it needs to happen right away. Let's take a look at some of the players who need to be replaced by their respective clubs.
#5 Moussa Dembele
When you have a brilliant midfielder solving all your midfield problems, its tempting to rely on him heavily.
But when you are trying to build a new stadium to establish yourself as one of the Premier League's top sides and that midfielder is 31 years old, you are asking for trouble.
Now that is the problem for Tottenham Hotspur with Dembele. A forward player at Fulham, the Belgian has turned into a reliable midfield player for Mauricio Pochettino's side, who can put in strong defensive displays and push Spurs into the final third with his dribbling.
But ever since the 2015/16 season, his minutes have become less and his defensive numbers in tackles and interceptions have gone from 5.7 a game to 3.5 a game to now 2.7 per 90.
Even with defensive partners like Eric Dier and Wanyama, that is a huge drop. Although Harry Winks can play in his position and fill the gap, he doesn't have the fitness.
With Harry Kane aged 25, Christian Eriksen 26 and Pochettino in his 5th season with the Spurs, it is time for Daniel Levy to bring out that cheque book if he wants to take some silverware into the new stadium.
#4 Edin Dzeko
The arrival of Monchi in Italy should see Roma as the place for young talent, but though the regeneration has begun in the wide areas and midfield, they still depend upon Edin Dzeko in the attack.
The Bosnian who cost Roma only €15 million in 2015, has scored a third of Roma's league goals but will turn 33 this season and you cannot expect him to keep banging them into the net for long.
While Roma has plenty of wingers in El Shaarawy, Justin Kluivert, Cengiz Under and Diego Perotti, their back-up for the striker position is a 22-year-old Patrick Schick, who at the time of writing has played just under a 1000 minutes with over a year with the team.
Currently, Schick has only 25 goals to his name, he lacks being the focal point of attack which Dzeko possesses but also creates only 1.4 chances compared to Edin's 1.6 chances per 90.
Schick being only 22 has plenty of time to improve but with the Milan clubs spending loads of money to improve their teams, its time for Roma to search for an able replacement.
#3 Fernandinho
As bad as an injury to Kevin de Bruyne or Sergio Aguero can be, it is Fernandinho who is indispensable to Pep's Manchester City.
Guardiola went into the summer of 2018 to find a long-term heir to his midfield general, but with failed moves for Fred and Jorginho, the Catalan has started the season with no reinforcements.
Now, this is a major problem because City depended a lot on the Brazilian last year and is already old at 33.
Vital on the defensive side of the ball, with five tackles and interceptions per game compared to Ilkay Gundogan's 3, Fernandinho is surprisingly influential in possession too.
Age is surely going to affect his fitness or form or sometimes both. It is high time City start searching for an able replacement or hope they don't lose out on the title because of this.
#2 Samir Handanovic
An amazing servant for Inter Milan, goalkeeper Samir Handanovic has quietly been one of the most consistent keepers around over the last few seasons.
Since he joined Inter in 2012, he has missed just nine games for them in the Serie A, playing a massive 219 out of 228, and he has made the divisions Team of the Year twice.
2017/18 has been probably the best season of his career, the Slovenian whose form has kept Jan Oblak to under 20 appearances for the national side.
He also conceded only 30 goals in Spalletti first season in charge, when expected goals were at 37, that seven-goal difference is the second best in Serie A, with Alisson saving 10 goals less.
Now at 34, Handanovic has reached the age when Cech, Casillas, Claudio Bravo all started to decline. Handanovic cannot be continuing at this level for longer and it is time for Inter to start searching for someone to fill the boots of the Slovenian stopper.
#1 Sergio Busquets
As sad as it might be, Sergio Busquets' days as the best defensive midfielder are numbered. He made his debut for Barcelona in 2008, the Spaniard has won seven out of 10 league titles he has competed for, as well as three Champions Leagues, a World Cup, two European championships and 18 other trophies.
However, Busquets is 30 years old now and his legs can't last forever. In 2017/18 the one club man had yet another spectacular season, winning the ball over five times a game and passing it into the final third eight times.
But his role is physically demanding, Busquets pressed an opponent at least 25 times a game and Barcelona lost just a single league match throughout the season.
The combination of his age and the requirements in his position mean that Busquets is likely to be more help going forward and Barcelona will need a new defensive midfielder for the long term. If only they snapped up Rodri before he joined Atletico Madrid.