The transfer window closed last week, with Arsenal signing Danny Welbeck from Manchester United for a fee understood to be around £16m on deadline day. But despite signing a much-needed centre forward, the Gunners are still short at the back as Arsene Wenger's side enters the season with just five senior defenders. Teenagers Calum Chambers and Hector Bellerin might feature prominently this term but the north London outfit is still short of bodies for the centre-back role.

However, fortunately for Arsenal, they can still add two more players to their Premier League squad before the January window opens; which basically means they can find a solution to their defensive worries (at least temporarily) with a free agent anytime. So let's take a look at the best four options Wenger has before him.

Diego Lugano (Uruguay)

Diego Lugano
Lugano was part of the Uruguay side which reached the round of 16 in Brazil.Reuters

The much-travelled Lugano, who was part of Uruguay's World Cup squad, became a free agent this summer after West Bromwich Albion decided to release him, after the first season of his two-year contract. The 33-year-old did not feature under Steve Clark in the first half last season but started to find some game time under his successor Pepe Mel, only to fall out of favour at the club again. The former Feherbahce star, who has 95 international caps to his name, is the youngest player on our list but not the ideal choice, especially with quite a few managers having expressed their dissatisfaction over his attitude and commitment in the past.

Carlos Marchena (Spain)

Carlos Marchena
Marchena spent the last two seasons with Deportivo.Reuters

Marchena presents himself as a valuable choice as he can play both as a centre-back and a defensive midfielder, which was the sort of player that Wenger wanted in the first place. The Valencia legend is known for his tackling, interceptions and reading of the game. However, the 35-year-old, who has spent his entire career in Spain, might not endure the rigours of the Premier League, especially after playing last season in the second tier with Deportivo de La Coruna.

Joseph Yobo (Nigeria)

Joseph Yobo
Yobo captained Nigeria at the World Cup, guiding them to the last 16.Reuters

Yobo brings in immense Premier League experience and reputation with him, having spent eight years at Everton. The 34-year-old has won 100 international caps for Nigeria and was very much part of the Super Eagles squad, which made it to the last 16 of the World Cup. Yobo returned to England for the second half of last season, joining Norwich City. And though the Canaries ended up being relegated, some of Yobo's performances stood out, especially the 1-0 win against eventual champions Manchester City in February. The Everton legend left Norwich by mutual consent in the summer and now becomes a decent option for Arsenal.

Mario Yepes (Colombia)

Mario Yepes
Yepes even put the ball in the back of the net against Brazil but it was wrongly ruled outReuters

Yepes had a brilliant World Cup with Colombia, and was surely one of the top three centre-backs in the tournament, alongside Argentina's Ezequiel Garay and Germany's Mats Hummels. The 38-year-old did not make a single error throughout the showpiece tournament in Brazil. Dominant in the air, always in the right positions and with a highly impressive distribution for a defender, Yepes stood out. The former PSG star's best performance came against Brazil in the quarterfinal, where he pretty much singlehandedly nullified the hosts in open play.

Yepes, who spent the last season with Serie A side Atlanata, is not getting any younger but looking at his performances at the World Cup, he surely has at least one good year left in him. If Arsenal can get him, he will surely be the best fourth choice centre back in the Premier League. It might also allow Wenger to try Chambers in a defensive midfield role, like he said when he signed the youngster.

Yepes is slow and might not work well with Per Mertesacker against teams which sit back and counter. But with Laurent Koscielny the Colombian can form a stellar centre-back pairing, while him and Chambers - if a crisis arises - will be more than decent as well. Yepes is old school but he is a rock. If Wenger is indeed looking to bring in a central defender for short-term cover, this should be a no-brainer.