As the January 2020 transfer window closes in, speculation is rife about Jadon Sancho and his future at Borussia Dortmund. After a dream start at the German club last season, various incidents, reports, and news this season seem to suggest that the England international is unsettled at the club and is looking for an alternative. He has been linked with the likes of Manchester United, Liverpool, Manchester City, and Chelsea.Frank Lampard was not able to spend in the summer, owing to the transfer ban put by FIFA on the club. Now that the transfer ban has been lifted and the London club is free to spend, Sancho is the type of player they would certainly be attracted to. Their potential to complete the transfer is also increased by the fact that along with Manchester City, they are among the few clubs who can afford the 19-year-old.So, keeping that in mind let's take a look at 3 reasons why Chelsea should sign Jadon Sancho.#3 Long term replacement for WillianWillian is coming towards the end of his time at ChelseaWillian has been at Chelsea since the 2013-14 season and has been one of the constants for Chelsea through a period where manager changes and player transfers were rampant. But with Frank Lampard promoting youth, it can be said that the Brazilian international might be playing in his last season at the club and it is a question of "when and not if" he leaves the club. Sancho is the perfect candidate to fill the void that would be left by the current Chelsea winger.To begin with, the duo can play on either of the wings, love running at the defenders and have tricks in their bag. Versatility is one of the traits that has helped the Brazilian survive at Chelsea under so many different managers and the fact that Sancho can easily adapt to a formation change makes him a good candidate to stay at any club in the long term.From a statistical point of view, the two wingers have completed almost 2 dribbles, provided 1 key pass, and have taken 2 shots in every match in the Bundesliga and the Premier League so far, suggesting the similarity in their sense of play.Furthermore, Willian has been fouled twice in every match vis-a-vis Jadon Sancho being fouled once in every Bundesliga game, suggesting that the defenders don't fancy giving an inch of space and time on the ball to the two players. Whenever time and space has been given to the two players, they've displayed their pace and trickery time and again.Chelsea FC v AFC Bournemouth - Premier LeagueAlso check out: EPL fixtures EPL table Champions League table