The Saints, who are second in the Barclays Premier League, face Aston Villa on Monday ahead of a testing month that brings games against Manchester City, Arsenal, Manchester United, Everton and Chelsea.
Koeman's side also have to play four games in nine days over Christmas including league fixtures on Boxing Day and New Year's Day before the FA Cup third round on the first weekend in January.
"It's difficult because I don't have experience playing that number of games in such a short time," Koeman said.
"I always used to be on holiday during Christmas and now we have a lot of games to prepare for.
"I told the players, 'honestly, I don't have that experience', it's difficult.
"We have to play December 26 and then again on the 28th, January 1 and then January 3 for the FA Cup - it's crazy.
"It's not crazy to play at Christmas because I understand - we had that in Holland and the people like that.
"I'd like that as well if I like football and support Southampton - I can have my Christmas meal then go to the stadium and watch Southampton, I am happy.
"The problem is you have one day off between two games and that's crazy, that's impossible.
"That's my problem with the schedule because if it's the 26th and the 29th, no problem, but it's Friday and Sunday
That's crazy, one day off, crazy."
Southampton have reaped the benefits of Koeman's consistent selection policy this season.
The Saints have started less players (15) in the league so far than top four rivals Arsenal (18), Tottenham (21), Liverpool (21) and Manchester United (22).
Koeman believes the fixture congestion at Christmas plays into the hands of those teams with bigger squads at their disposal.
"Does it favour the big clubs? Yes
They can change players much easier than other teams in the Premier League," Koeman said.
"It is worst for the clubs who haven't got 24 players at the same level.
"You have to change your team and I don't like to change my team
I believe if the team is doing well you can change one or two positions but I don't believe in changing my team in six or seven positions."
If Southampton want to keep pace with the sides at the top of the table, they may need to bolster their options in the January transfer window.
"Our transfer policy in January doesn't depend on winning and losing over the next month," Koeman said.
"It depends on the players we have - for example we know that Sadio Mane has to play at the African Nations Cup, Maya Yoshida will play in the Asian Cup but we don't need a lot of players.
"I am happy with the players we have
It depends on injuries if you need someone but it's too early to make conclusions about that."
Source : PA
Source: PA