To cover that hypothetical, here is a scouting report of Vargas.
Vargas' 2014 FIFA World Cup Summary
Starting up front, Vargas scored and created a combined 0.75 goals per game at the World Cup, which was substantially higher than his La Liga average (0.24) on loan at Valencia last season.
That said, Vargas needed to be more active.
Vargas ranked in the bottom three in distance covered for outfield starters in every single one of Chile's World Cup games, per FIFA.com.
Greek attacking midfielder Lazaros Christodoulopoulos took the same amount of shots in one game against Ivory Coast (four) as Vargas did in the entire tournament.
While Vargas was statistically solid—one goal and two assists in four games—he did not have the same impact for Chile as James Rodriguez has had for Colombia.
|Eduardo Vargas||James Rodriguez|
|Shots Per Goal||4||2.8|
|Key Passes Per Game||0.8||2.0|
|Dribbles Per Game||0.5||2.5|
Vargas is pacey, excels at getting into the penalty box, is a threat on the counter-attack and can poach goals.
Rising high to meet Valencia attacking midfielder Daniel Parejo's corner, Vargas headed the ball past Getafe goalkeeper Jordi Codina.
Latching on to Valencia attacking midfielder Sofiane Feghouli's lobbed through ball, Vargas slashed his way past Almeria centre-backs Angel Trujillo and Marco Torsiglieri, to score.
Accelerating past Real Betis right-back Juanfran, Vargas controlled the ball with his chest before striking it on the half-volley past Betis goalkeeper Antonio Adan.
In Vargas' last three combined European seasons, he scored three goals in league play.
All 19 of Vargas' appearances for Napoli were as a substitute, which is why he sought a detour to play in Brazil with Gremio.
Last season, on loan at Valencia, he went through long stretches of games without making a meaningful impact.
Vargas' shooting accuracy was below average (44 percent, per Squawka.com), and he was an inefficient scorer—registering just three goals from 28 shots.
What about Vargas?
Napoli are open to letting him go, per Football Italia, so he could be another project Wenger takes up.
However, Vargas being a transfer bust in Europe is a major red flag.
His career is imitating compatriot Jorge Valdivia: talented enough to play for an elite European club, but lacking the intangibles to thrive there.
Napoli signed Vargas winning race over Chelsea and Inter,which yesterday made a last minute better bid anyway rejected (via @lgbucciCNN )— Tancredi Palmeri (@tancredipalmeri) December 21, 2011
Statistics via WhoScored.com