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He was part of a transfer triangle that saw Pierre-Emerick Aubameyang go to Arsenal, while Chelsea signed Olivier Giroud, allowing Antonio Conte to release Batshuayi to earn more game time ahead of the World Cup.
Batshuayi signed for Chelsea for £33.2 million, but he has struggled to earn the trust of his manager since moving from Marseille. His impressive start to life at Dortmund has, however, proved he is capable of having a big impact.
He has been in and out of the team having made 17 starts with a further 10 substitute appearances, but he is very highly regarded having made his England debut in 2017.
Abraham is quick, a good finisher and has been working on his build-up play at the top level. His performances have significantly contributed to Swansea's season and his loan move to Wales has to be regarded as a modest success.
The Scottish champions have him on an 18-month loan deal after he renewed his Chelsea contract and he will be hoping that a longer spell with the Hoops can earn him a similar level of experience to that of Andreas Christensen, who is now a first-team regular at the club.
Musonda has already started more games for Celtic than he did for Chelsea having joined on loan in late January, but he has yet to establish himself as an automatic starter.
Mason Mount is making a huge impact in the Eredivisie and has got into the team of the week several times since the turn of the year.
His performances with Vitesse are remarkable for a player who has just turned 19, and he has contributed seven goals and three assists this season.
Mount was crowned the player of the tournament as he helped England to glory at the UEFA European Under-19 Championship in the summer.
Kenedy had a tough spell on loan at Watford where he was plagued by injuries and although he was in Antonio Conte's first-team squad this season, he rarely played and was behind Marcos Alonso in the pecking order.
Since his temporary move to Newcastle United he has been moved further up the pitch and that has seen him flourish, with his direct running and intelligence in the attacking third seeing him thrive on Tyneside.
Chelsea will be watching closely as the 22-year-old looks to get back on track following a tumultuous start to his Blues career, with off-the-field issues contributing to a disappointing start.
Chelsea have welcomed the midfielder back at their training ground for him to recover, but it is hoped that he can return for Palace before the season is out and perhaps even force his way into the Three Lions squad for the World Cup.
Loftus-Cheek is one of the jewels of Chelsea's academy and is highly regarded, but he will need to now push on and keep proving himself at the highest level to earn a place in the first team at Stamford Bridge.
Ola Aina broke into Chelsea's first team last season making six appearances after impressing on a pre-season tour of the United States.
However, having only made two starts, it was clear that Aina needed a loan move and he has performed brilliantly during his time at Hull City this season.