This weekend has seen a series of upsets in the Copa America. Colombia were knocked out by Peru. Hosts Argentina were dispatched by Uruguay. Brazil lost a penalty shootout to Paraguay, and Alexis Sanchez's Chile were somewhat inexplicably seen off by Venezuela. With Uruguay as the only real powerhouse left in the tournament, that means that a lot of good players are on their way home.

David Luiz and Ramires will presumably be rejoining Chelsea during the club's tour of Asia (the fact that Brazil refused to give David Luiz any playing time at all in the tournament means that, in my opinion, they deserved to go out on penalties), but the fate of many other returning stars is unclear. Several key players' collective futures are unknown, including Chelsea targets Neymar, Sanchez and Javier Pastore.

The Copa had served as something of a barrier to the continued transfer saga of all players competing. All major deals were put on hold as the competition unfolded - I think the only news to go through while a player was still active was Radamel Falcao's contract extension with FC Porto, and that doesn't really count. Now most of the big names are out of the tournament, and they seem to have wasted little time with the moving around. Carlos Tevez and Sergio Aguero are both in play, the former moving (I don't get it either) to Corinthians for almost 40M, with Kun Aguero expected to take his place at the Etihad Stadium.

There's another Argentinian in the mix in terms of player movement, however. Palermo midfielder Javier Pastore is widely expected to move on in this transfer window, and Chelsea are known to be in the mix for his services. Now that the hosts' tournament is over, expect that particular rumour thread to heat up significantly.

Chelsea, of course, are also known to be hot on the heels of another talented midfield playmaker - one Luka Modric. The need for some reinforcements in the centre is patently clear, especially in the light of the season-threatening injury incurred by Michael Essien, and the club is almost certain to splash some cash to bring new faces in. How much cash is another question entirely.

Despite not knowing just how much money Chelsea can spend, I think it's probably safe to assume that we can't afford both Modric and Pastore at the same time (although it certainly sounds like fun!). With that in mind, why not do a little bit of comparing and contrasting? Might as well pick our favourite now. Let's do this.

Javier Pastore vs. Luka Modric Age: 22

Position: Attacking midfielder

Current Team: Palermo (Serie A)

Expected Price: £40M+

Champions League Experience?: No

Premier League Experience?: No Age: 25

Position: Central midfielder

Current Team: Tottenham Hotspur

Expected Price: £30M+

Champions League Experience?: Yes

Premier League Experience?: Yes Pros Pastore is the centrepiece of an exciting Palermo side and widely considered to be the heir to Kaka as the world's top trequartista.

At 22 years old (and barely, at that) there's plenty of time for him to develop further, and he's already an excellent player, with an exquisite understanding of the game.

Position he takes up is very similar to Frank Lampard, who'll need to be replaced shortly.

Only 'blocking' Lucas Piazon, who's years away from becoming a sure thing.

Pros Modric is an accomplished Premier League player with Champions League experience, carries a Tottenham team that relies on his disciplined passing from deep.

A fully developed player, needs no projection to be a major force on a Chelsea team particularly weak on the midfield creativity.

Buying Modric would make Tottenham immensely cranky, which comes with many benefits - as well as weakening a rival.

Significantly cheaper than Pastore's anticipated price, wants to join Chelsea.

Cons Pastore looks like he could be a future Ballon d'Or winner - and Palermo want Chelsea to pay the associated cost. He's going to be very expensive.

No Premier League or Champions League experience means that a rough transition is very possible. Chelsea have a good record with Italian imported, but for the rest of the league results much worse. Combined with price, the risk is very high.

He's currently a little inconsistent, and needs to grow out of that. Should be an experience/maturity thing.

Cons Tottenham are resisting any sale of their best player, and with several years left on a club-friendly contract have no reason to sell other than the player's wishes. Spurs will fight extraordinarily hard to keep him or raise his price to as high as possible.

Acquisition of Modric would likely force Chelsea into a system switch, which may be disruptive. Would also push one of Ramires and John Obi Mikel out of starting lineup while leaving problem player (Lampard) as first choice.

Blocks top prospect Josh McEachran.

It would be tempting to look at that and come up with a definitive answer, but I've stared and stared and stared and nothing's happening. Honestly, both are exquisite players and I'd love to see them moving to Stamford Bridge. Pastore and Modric bring slightly different packages to the table, but they're both absolutely superb players. Modric is the more obvious choice if you want to win in the here and now, while Pastore is a better long term bet, but I should probably emphasise that Pastore will be very good in the short term as well, and so will Modric in the long.

In other words, I can't decide between them. I think I slightly favour Pastore right now, for reasons I can't really articulate, which means that they're probably stupid. There's just nothing separating the two from where I stand. But when Chelsea are associated with players of this sort of calibre, life's looking pretty good, eh?