An already thin U.S. group of forwards just got thinner as striker Jozy Altidore was escorted off the field with a hamstring injury in the Americans’ opening match of World Cup 2014 against Ghana.

In about the 23rd minute, midfielder Michael Bradley sent a long ball to Altidore along the left side. The 24-year-old immediately grabbed his left hamstring and winced in pain.

The medical team then rushed onto the field and carried Altidore to the sidelines, prompting head coach Jurgen Klinsmann to choose Aron Johannsson as the substitute forward.

Things threatened to get worse for the U.S. when Dempsey later took a foot to the face, and had to head to the sideline with a bloody nose. With Dempsey being treated, Chris Wondolowski was seen jogging along the sideline in the event that Dempsey couldn’t return.

Dempsey did return to action, but concern continues to surround Altidore.

It is difficult to determine a player’s time frame for return from a hamstring strain. It remains possible that Altidore could have a very speedy recovery.

But the injury poses a dilemma for Klinsmann, as Altidore is the only target-man striker on the roster. Johannsson is just 23, and entered the World Cup with less than 10 caps. Wondolowski is a veteran at age 31, but this is his first World Cup, and he has limited experience against elite competition. With Altidore the clear first-choice striker, neither Johannsson nor Wondolowski were expected to receive significant minutes.

The situation prompts questions about Klinsmann’s rather controversial decision to leave Landon Donovan off the U.S. roster. The omission of Donovan, who has been one of the most valuable players for the U.S. in the previous three World Cups and is regarded by many as the greatest American player of all time, raised eyebrows across the country. In recent times, though, Donovan had largely been used as a wide midfielder at the international level.

There remain options for Klinsmann to modify his lineup. Dempsey could move to being the main target-man, with an extra attacking midfielder added. Julian Green would be a possible, but highly unlikely option from the start. The 18-year-old’s inclusion to the roster spoke highly of the lofty expectations surrounding the German-born talent, but he has played just one senior game at club level, although that club is German champions Bayern Munich.