Chelsea have sanctioned hundreds of loan deals throughout the Premier League era.
The task of monitoring them became so big that the club even created a new role to oversee all those temporarily playing their football elsewhere.
As we have seen in 2019/20, loan moves can be hugely beneficial to players who subsequently return to Stamford Bridge with more experience under their belts.
Here are six Chelsea stars who were much better off for a period out on loan.
Tammy Abraham (Bristol City, Aston Villa)
Abraham spent a season in the Premier League with Swansea but two spells in the Championship either side of his Liberty Stadium stay were more significant for his development.
The striker had played only two games for Chelsea before joining Bristol City at the start of the 2016/17 campaign.
Abraham was a major success for the Robins, scoring 23 goals in 41 games to help them avoid relegation to League One.
He was even more prolific at Villa in 2018/19. Abraham scored 25 goals in just 37 Championship appearances as Dean Smith’s side secured promotion back to the Premier League.
That haul convinced Frank Lampard to make Abraham his first-choice No.9 this term.
And the striker has made the step up look easy, notching 13 times in 25 top-flight matches and establishing himself as Chelsea's top scorer.
John Terry (Nottingham Forest)
Terry only played six league games for Forest in 2000, but his brief stint at the City Ground was nonetheless integral to his development.
The future Chelsea captain had already played a handful of matches for the Blues but was finding it difficult to nail down a regular starting spot at Stamford Bridge.
Playing competitive football in the second tier, albeit for a brief period, helped toughen Terry up.
It was particularly useful given his position: young centre-backs find it particularly difficult to break into Premier League line-ups.
Terry did just that the following season, and went on to win no fewer than five Premier League titles in west London.
Mason Mount (Vitesse, Derby)
Chelsea’s relationship with Vitesse has seen numerous youngsters spend time with the Dutch club at an early stage of their development.
Mount was perhaps their most successful temporary import. The midfielder spent the 2017/18 campaign in Arnhem and won the club’s Player of the Year award at the end of it.
He was also a regular in the Eredivisie team of the week as Vitesse finished a respectable sixth.
Mount then joined Derby the following year after Lampard was appointed their manager.
The England international scored 11 goals in all competitions and helped the Rams reach the Championship play-off final.
Lampard has continued to play him regularly back at Stamford Bridge, with Mount having made 41 appearances in 2019/20.
Fikayo Tomori (Derby)
Tomori also spent the 2018/19 season on Derby’s books as Lampard made the most of his Chelsea connections.
The defender had previously played on loan at Brighton & Hove Albion and Hull City, but it was at Pride Park that he convinced Chelsea he had a future at Stamford Bridge.
Tomori played 55 games in all competitions, an incredible amount for a centre-back who hadn’t even turned 22 at that point.
The Canada-born defender won Derby’s Player of the Year award as the Rams narrowly missed out on promotion to the top flight.
Tomori had to be patient for game time at the start of 2019/20 but an injury to captain Curtis Davies saw him soon become a regular at the heart of the Chelsea defence.
Daniel Sturridge (Bolton)
Chelsea snapped up a 19-year-old Sturridge following the expiration of his Manchester City contract in 2009.
The striker arrived with a glowing reputation and scored five goals in his debut campaign at Stamford Bridge.
Sturridge spent the first half of 2010/11 in west London but was then loaned to Bolton in the January transfer window.
He was a huge hit at the Reebok Stadium, netting eight goals in 12 Premier League games as Bolton flirted with a top-eight finish.
Sturridge may now be more readily associated with Liverpool than Chelsea, but he helped the Blues win the Champions League and FA Cup the season after his spell at Bolton.
Ruben Loftus-Cheek (Crystal Palace)
Injury has prevented Loftus-Cheek appearing for Chelsea so far in 2019/20, but he’s expected to be a big part of Lampard’s team going forward.
The midfielder has already played 22 Premier League matches for the Blues before his season-long stay at Palace in 2017/18.
Nevertheless, the experience he gained at Selhurst Park undoubtedly made him a better player.
When fit, Loftus-Cheek was one of Palace’s standout performers that season. His performances for Roy Hodgon’s side even earned him a place in England’s World Cup squad.
Loftus-Cheek returned to Chelsea the following year and made 40 outings in all competitions under Maurizio Sarri.
