Exeter coach Rob Baxter has been the recipient of much praise for his over-achieving squad.
"They seem a great bunch of guys, the work ethic is brilliant," said Horstmann.
"You can have good banter in the changing room, but when it's time to work people knuckle down and work hard. It's the ability to chop and change which is really good.
"You can feel the energy of them working around each other and there's a great team spirit amongst them. If you could bottle it you could make an absolute fortune. Creating that team spirit certainly isn't easy, but it's something Rob's created here and I think he should be very proud because the boys have got a huge amount of self-belief."
Exeter's Rob Baxter received the Premiership's director of rugby award for the 2011-12 season.