Gareth Southgate believes English players have been hampered by the Premier League starting so soon after the World Cup.
England's top flight began on Friday August 10, less than a month after England had been knocked out by Croatia in the semi-finals in Russia.
The first divisions in France and Italy began on the same weekend, but La Liga in Spain kicked off on August 17 and the Bundesliga in Germany on August 24.
"When you see the league, a lot of teams haven't started yet at their maximum. There have been lot of injuries across our league," Southgate said on Sunday.
"I don't really understand why our league started so early, but they did, and it was a really difficult situation for the clubs.
"Some of the clubs couldn't field a team without...look at Tottenham, who had so many players in the semi-finals of the World Cup.
"It was an impossible situation for their coaches really.”
England face Spain in the UEFA Nations League on Monday, hoping to improve on their 2-1 defeat at Wembley last month, when the scoreline did not do Spain's dominance justice.
Spain then thrashed Croatia 6-0 and can seal top spot in Group 4 with a victory in Seville, while England are scrapping to avoid relegation.
"We know their technical ability," Southgate said. "But we have to cause them problems with the ball. We can't just defend for 90 minutes.
"We were more comfortable in the last 30 minutes at Wembley, but we have to do that earlier in the game, be brave enough to use the ball well, and cause them problems."
England have switched from a three to a four-man defence since the World Cup, in an attempt to exert more pressure higher up the pitch.
Spain have also changed tack under Luis Enrique, who has instilled a more direct, attacking approach since taking charge following the disappointing performances at the World Cup.
"Their style is a little bit different now, they've got a new coach, a top coach," Southgate said.
"Although the style and the philosophy is very similar, tactically it's a bit different. There is a bit more of a direct threat in the final third.
"It's as big a test as you can get in European, if not world football, at the moment."
Southgate confirmed Liverpool defender Joe Gomez will replace the suspended John Stones in defence. Jordan Henderson is also serving a ban.