Although it is unlikely that both sides will put out their strongest possible lineups (in fact, expect far from it), the Barcelona list of reserve talent is still far superior to the standards of the teams United have played so far during their preseason.
La Masia has been the breeding ground of some of the modern era’s greatest players. You need look no further than the current bevy of Barcelona players to see exactly how successful the famous Spanish youth academy is at churning out the world’s best.
Messi, Xavi, Puyol, Iniesta, Busquets, Pique and Fabregas are just a short list of players who at one time or another passed through the Masia doors and onto greatness.
Looking to the future, players such as Christian Tello, Isaac Cuenca and Thiago Alacantra are now starting to pave the way for the second great generation of Barcelona within just the past decade.
These are the types of players that United, and Kagawa, will have to primarily reckon with later on tonight.
Let's not get carried away—how Kagawa fares against this Barcelona side will far from make or break the Japanese International’s United career.
However you slice it, this match is still just a friendly, and has no real bearing on anything come the official start of the 2012-13 season this Saturday—when Chelsea take on Manchester City in the Community Shield.
But, if Kagawa can go out there and rub shoulders with the mixture of Masia and experienced Barcelona first-teamers—who are sure to include Lionel Messi and the returning David Villa—then it will really begin to validate the faith that Fergie has put in the former Borussia Dortmund midfielder.
This is the perfect opportunity for Kagawa and the rest of the United side—both first team and reserve—to build confidence going into their clash against Everton at Goodison Park on August 20.
This isn’t the Red Devils' last friendly before then, but it is their most important one in terms of genuine preparation.
If Kagawa gets a decent amount of game time and performs as well as we all know that he can, then the chances are high that the 23-year-old will approach the new season with an even greater vigour than one might already expect.
A good performance against any Barcelona team, whatever the circumstances, is always something for any footballer to boast about and take extreme reassurance from.
Ultimately the result is unimportant. But, at this stage, United really should be looking for good performances from the players they expect to rely on during the 2013 season.
Can Kagawa be one of these players come the 20th?
This game might be the first real hint at an answer to that question.