The January transfer window is always more tricky than its summer counterpart.
Play your cards right, and you could get just the boost you need for the rest of the season or even make a clever investment that can serve the team for years to come.
Here are our top 10 January signings in the Premier League era.
10. MIKEL ARTETA | REAL SOCIEDAD TO EVERTON | £2M
Arteta helped Everton to a fourth-place finish following a loan move in January 2005. The Spaniard settled in seamlessly and David Moyes ensured the move was made permanent that summer for a bargain.
9. PATRICE EVRA | AS MONACO TO MAN UNITED | £7M
Evra initially struggled following his arrival in 2006 but went on to establish himself in the first team. He became a fan favourite over the years, winning five league titles and one Champions League.
8. GABRIEL JESUS | PALMEIRAS TO MAN CITY | £27M
Guardiola may have splurged on defenders at City but Jesus was one of his shrewder purchases. The young Brazilian striker hit the ground running, scoring seven in his first 11 appearances and hasn't looked back.
7. JAVIER MASCHERANO | WEST HAM TO LIVERPOOL | £18M
Rafa Benitez's inspired signing of Mascherano in 2007 to partner Xabi Alonso and Steven Gerrard formed one of Liverpool's finest midfields, nearly ending their long wait for a league title.
6. NEMANJA MATIC | BENFICA TO CHELSEA | £21M
Jose Mourinho raised eyebrows when he spent heavily to bring Matic back to the Bridge but the decision proved to be right as he was the foundation on which Chelsea's 2014-15 title-winning team was built.
5. HENRIK LARSSON | HELSINGBORG TO MAN UNITED | LOAN
He only scored three goals in his 13 appearances for United but his presence, link-up play and overall contribution boosted the team during a key juncture of the 2006-07 season... for no fee.
4. GARY CAHILL | BOLTON TO CHELSEA | £7M
After signing in 2012, Cahill remarkably went on to win all six tournaments Chelsea participated in at least once. He helped ease the transition as John Terry played sporadically and eventually left.
3. PHILIPPE COUTINHO | INTER MILAN TO LIVERPOOL | £8.5M
Coutinho joined the Reds in 2013 and has since risen to stardom. The Brazilian magician wowed Premier League audiences and was named Liverpool's Player of the Year in the last two seasons before Barcelona came calling.
2. NEMANJA VIDIC | SPARTAK MOSCOW TO MAN UNITED | £7.2M
Vidic's fearless no-nonsense approach perfectly complimented Rio Ferdinand and duo went on to forge a centre-back pairing that dominated Europe during one of the club's most successful periods.
1. LUIS SUAREZ | PSV TO LIVERPOOL | £22.5M
Suarez arrived at Anfield in 2011 in Andy Carroll's shadow. After a record of 82 goals in 133 appearances though, he achieved legendary status, drawing comparisons to Liverpool's greatest ever players. Carroll, well, didn't.