The 26-year-old Manchester City forward was substituted after 67 minutes as Norway lost 2-1 away to Portugal in Nations League Group A4 on Sunday.
Haaland was among several high-profile players who left the stadium straight after the match on a private jet to make the most of a brief holiday before returning to club duties.
"He was simply thoroughly spent," Norway manager Stale Solbakken said of Haaland's condition.
"Some of my players have only had six or seven days of holiday. And you do not live off your physical condition in a normal job. Then it is straight into the start of the season, followed by a mini-tournament, so it is an extreme strain."
"He’s in the group that carries the heaviest workload - precisely because his team (Manchester City) plays in every tournament and he’s the main man," Solbakken added.
Norway midfielder Patrick Berg echoed his manager's assessment, noting the physical toll on Haaland.
"He has played all three (Norway) games before this one, so it's not that shocking his strength finally ran out," Berg said.
Haaland has endured a gruelling schedule in recent months. Norway's run to the World Cup quarter-finals significantly cut short his off-season, and he has since featured in every Premier League match for City, scoring five goals.
Haaland highlighted the relentless schedule on social media after a two-goal performance in the 3-2 Nations League win over Denmark last month, posting: "So tired. New match in 70 hours."
Union concerned
Norwegian players' union NISO expressed concern over the escalating match schedule for the country's leading athletes.
"Over time, we have seen a worrying trend where the burden on top players has become far too high," NISO chief Kristoffer Vatshaug said in a press release on Monday. "It has already had consequences for several players. This is serious.
"We want clearer guidelines for workload and recovery. It is about the time between matches, consecutive rest periods, travel strain and how much time players get to recover after a long season."
Vatshaug said the responsibility does not rest with individual players.
"We cannot have a system where protecting players depends on them saying stop themselves. Footballers want to play football. They want to turn out for their club, national team and teammates."
Haaland has six days to recover before City resume their Premier League campaign at Liverpool on Sunday.
UEFA Nations League
The UEFA Nations League 2026/27 is contested by the national teams of 54 of UEFA's member associations. They're divided into four leagues based on the rankings of the previous edition, with Leagues A, B, and C featuring sixteen teams each, divided into four groups of four, while League D features six teams divided into two groups of three. It begins in September 2026, with the finals in June 2027.
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