After Spain's surprising loss to Japan in their opening fixture, their next match against Honduras is a must win.
Spain's Olympic squad has some big names on it, but the performance against the Japanese U23 side highlighted the fact that when it comes to U23s, Spain do not possess the dominance they do at the senior international level.
That is, as long as you aren't a Spain fan, a good thing. The football at this year's tournament is going to be far from perfect, yet highly exciting and far less predictable than other international tournaments.
Honduras, meanwhile, had to settle for a single point against Morocco in their opening fixture, surrendering a second half lead and failing to capitalize on their opponents having a man sent off.
Highly touted Spain will be looking to take out their anger on the relatively unheralded Honduran side, but may well run into more resistance than they might have expected.
Here are five of the key clashes that will help decide this important Group D tie, which kicks off on Sunday, July 29, at 19:45 BST.