The performance was the worst since the Argentinian replaced Nigel Adkins at the helm in January and brought an abrupt end to a six-match unbeaten streak.
"From my point of view we just didn't start in the game," Pochettino said. "We didn't really get into the game at all.
"We didn't feel comfortable, especially when we conceded the first goal in the sixth minute.
"Then we became a bit fearful of their attacking strikers, who were quite fast, strong and physically fit.
"From that point on we were uncomfortable and never really got into the game.
"I think we had a bad day but, then again, the good days, the good victories and bad days give me a lot of information as a manager so I have learned a lot from today."