A big couple of transfer windows lie ahead for Chelsea and manager Maurizio Sarri.It's become abundantly clear this season that the Blues' squad needs revamping, such as finding a successor for Gary Cahill and replacing Alvaro Morata.Defensively Chelsea haven't been too bad in the Premier League - they've only conceded 16 goals in 21 games - but going forward they've struggled somewhat.Eden Hazard is their top goalscorer on a respectable 10 goals, while Pedro (six), Alvaro Morata (five) and Willian (two) only have 13 between them.Chelsea have scored the least goals (36) out of the top six and it's Willian's contribution that's most concerning.The Brazil international has only scored twice and provided three assists in the Premier League, which is poor for a forward of his calibre.His disappointing form has forced Chelsea fans to question whether he's good enough, so when news emerged that Barcelona were interested in signing him this month, they chomped at the bit.Per the Daily Mail, Barcelona submitted a player-cash-deal worth £50m for Willian that would have seen Malcom, who they only signed last summer for £38m, head in the opposite direction.Chelsea rejected the approach on Thursday evening, though, leaving the club's fans frustrated and wondering why they decided against it.Cue the Telegraph's Jason Burt, who has detailed the two reasons why Chelsea snubbed the chance to sign Malcom, 21, and make another £10m in exchange for Willian."Even though Willian has just turned 30 and only has 18 months left on his current contract, Chelsea value him higher than the proposal that was put to them by Barcelona representatives on Thursday," wrote Burt."Chelsea regard Willian as a key member of their squad and are looking to strengthen this window, rather than let first-team regulars go."So there you have it - Chelsea think Willian, 30, is worth more than £50m and they don't want to lose a key player, despite the fact they'd be getting a top talent in return.Chelsea fans have been reacting to the revelation and it's safe to say they're stumped. Check out a selection of tweets below.