Dele Alli must start for Tottenham against Manchester United

Prior to the 2008-09 season, Tottenham Hotspur scored 33 goals and conceded just 5 over the course of seven preseason matches, including big wins over Celtic, Borussia Dortmund, and Roma. As former manager Harry Redknapp never ceases to remind us, Spurs started that season by taking only two points from their first eight games. The lesson? Making grand conclusions based on preseason results is a fool's game.

Even so, preseason is still an important time for managers to evaluate their players, particularly when there is no clear cut starter for a given position. This is the situation Mauricio Pochettino finds himself in ahead of Saturday's season opener against Manchester United. With Ryan Mason still recovering from a knee injury sustained on England duty, Pochettino must determine the best midfield partner for Nabil Bentaleb on the basis of a few preseason appearances.

His two options could hardly be more different. Eric Dier has played a few games in central midfield while at Sporting Lisbon, but is primarily a centerback by trade. New signing Dele Alli, meanwhile, is most well known for his incredible goal-scoring record in League One.

The resulting narrative is predictable; Dier is the defensive option and Alli is the attacking option. It's also wrong. It does, however, illustrate a common misconception about football: that a player's defensive actions alone determine how much he contributes to defending.

In Dier's case, a tendency to sit deep and break up play is negated by loose passing and a poor first touch. As this GIF illustrates, the worst defensive action is sometimes an attacking action.

Real Madrid left back Marcelo pounces on Dier's poor first touch, which directly leads to a quality chance for Jese. This is especially problematic against Manchester United, the Premier League's highest pressing team last season. Dele Alli, in contrast, looks comfortable receiving the ball under pressure.

See ya later, Luka!

Bye, Toni!

Though these nutmegs are traditionally regarded as attacking or possession actions, they can also be thought of as defensive actions. Just by virtue of not giving the ball away, Alli has prevented a Real Madrid counter-attack. Part of the reason Sergio Busquets is regarded as the best defensive midfielder in the world is because he never gives the ball away.

Apart from his possession skills, the other issue with Dier starting on Satuday is his tackling, which is much rougher than that of a typical defensive midfielder. Against Real Madrid, he did this:

Good central midfielders avoid slide tackling in all but the most desperate of circumstances. Aside from risking a red card (and this certainly could have been called one), slide tackling is dangerous because it's all or nothing. Failing to win the ball can leave the rest of the team fatally exposed. Dier made a similar tackle against the MLS All-Stars. Starting Dier before he's cut these reckless challenges out of his game would be foolhardy.

Alli is hardly a perfect fit next to Bentaleb. His natural tendency is to get forward at every opportunity, which risks leaving gaps in midfield. Even so, he is very much a central midfielder, not an attacking midfielder playing out of position. Playing him alongside Bentaleb, with Mousa Dembélé just ahead in a forward destroyer role, would give Spurs three mobile, athletic players capable of keeping possession under pressure and pressuring United's midfielders in turn. It would also give Spurs their best chance of winning.