Vicente del Bosque believes that the injuries to Alvaro Arbeloa and David Silva complicated matters for Spain in Tuesday's World Cup qualifier against France, which ended in a 1-1 stalemate.
The Manchester City star was forced off after only 13 minutes of play due to a muscular problem, while the Real Madrid defender followed suit after the interval, much to the dismay of Del Bosque.
"The injuries were an immediate misfortune because it prevented us from managing the changes," Del Bosque was quoted as saying on the official Fifa website.
"In the first half we had control of the game and perhaps we lacked a bit of penetration with the missed penalty by Cesc and the other chance that Pedro had.
"The home and away games against France have always been dangerous for us. What will happen with the rest of the games I don't know.
"It seems March already will be important, but we can't take anything for granted with the other teams in the group as they will all aspire to be first."
Meanwhile, Juanfran, who replaced Arbeloa in the second half, has admitted that he was at fault for Olivier Giroud's late equaliser.
"I demand a lot of myself and I always think things could be done better. If I whack the ball out of play then the game ends there, but they counter-attacked, crossed and an unmarked player scored."
Spain resume qualification action on March 22, 2013, when they host Finland, before travelling to France four days later.