Wenger's response was brief. "It was the selection of the day," he said. Was there any medical reason? "No, no, no, no."
That was it on the subject. No one probed the rationale for excluding the £30-million-plus summer acquisition, source of the club's second highest transfer fee, who had already scored four goals for Arsenal account.
James McNicholas (@Gunnerblog) raised this question and offered some potential reasons in his ESPN FC blog post "Sanchez Error Tops the List of Questions to Ask Wenger." I'm drawn to a related but broader question, "How do you weigh the risk tradeoffs when you structure and select a starting XI?"
This strikes me as a legitimate and germane line of inquiry. Legitimate because, unlike transfer dealings, injuries, finances, and many other issues, the matchday construction of the team falls entirely within the manager's control; that's his core responsibility. It's a germane question because the team soon goes to Chelsea, site of last season's tactical disaster and mauling.
Deliberating risks in the tactical system
The experience at Chelsea, Liverpool, and Everton and continued signs of vulnerability to counterattacks should be provoking serious deliberations among the Arsenal manager and his assistants. In particular, they should be weighing the risks of sending both fullbacks into the attacking half of the field against the downsides of instructing them to remain in defensive territory.
More astute and experienced tactical observers than I have noted that Wenger has chosen the more assertive approach for years. It's still worth asking whether the benefits of extra players at the offensive end, such as the potential of outnumbering the opposition on the flanks, warrant the consistent and therefore predictable forward presence of Arsenal fullbacks. Against some opponents, those advantages are probably worth the risk; against speedy and precise opposition, perhaps not.
Assessing drawbacks to subtle structural changes
A second major tactical risk grows out of the new 4-1-4-1 formation. My colleague Michael Price has argued convincingly in "A Look at Arsenal's Move to the 4-1-4-1" that this change is a response to the pressing and counterattacking that overwhelmed Arsenal in away games against top opposition last season.
The 4-1-4-1 setup could mitigate that risk in the long run as it allows Arsenal players to close down the opposition more quickly. However, it's not a comfortable or fully formed system yet, so for the moment it heightens the risk that the defense will be overrun, particularly if the fullbacks' forays forward continue.
The manager has said that the formation represents only a subtle shift, and indeed it morphed comfortably and successfully into a 4-2-3-1 in the wins against Aston Villa and Galatasaray. In some ways, though, the subtlety only heightens the risk. That's because the players have to understand and execute the approach at a fine level of nuance. These mental and physical demands come on the heels of a World Cup, which taxed most of Arsenal's first team and shortened the period to hone this new approach.
Given that the 2013-14 system produced 79 points and an FA Cup, it's reasonable to ask whether the risks of the new system are worth taking on.
Balancing risks in team selection
The personnel available to the manager, even in light of multiple injuries, creates another series of risk tradeoffs.
The threats of being outnumbered in midfield and the defensive zone could, for example, be dealt with by moving the wide forwards closer to the back line, which is an approach we saw late in the 2012-13 season and early in the 2013-14 campaign. The risks in that are passivity and ceding possession, but the speed of new players Sanchez and Danny Welbeck and the returning Theo Walcott would worry the opposition even if it does control the ball.
Let's accept, though, that Wenger prefers a more proactive approach, and his knowledge, success, and teams' flair make me hesitate to question that philosophy. What I would nevertheless ask about is the omission of Sanchez from the starting XI, especially given the objectives of the evolving system. If the 4-1-4-1 seeks to follow Pep Guardiola's Bayern Munich and its coordinated pressing, doesn't Sanchez seem the perfect player to harry the opposition from a wide forward position?
Perhaps the balance Wenger was trying to strike against Tottenham was between what his team did with the ball and what it did without it. As Tim Stillman (@LittleDutchVA) observed in his weekly column for Arseblog last week, Sanchez attempts daring moves that often result in losing the ball. If the manager is prioritizing ball retention over offensive creativity, then that's a case for leaving Sanchez on the bench. It's also a reason to leave out Jack Wilshere in favor of Santi Cazorla in midfield, but Wilshere got the start against Tottenham.
These decisions have faded from view after the team's exhilarating performance against Galatasaray. That game -- and the role Sanchez played in it -- makes a compelling argument that his playing style represents a risk worth bearing. Otherwise, we'd have to entertain the possibility that the club spent more than £30 million on a player before its manager reached the conclusion that his style is too cavalier. That seems like an even more worrying proposition.