Rangnick was pleased that his side fought back against Koeln...
"We cannot continue to play as we did in the first half," he said to Kicker.
"We were very weak. We still had chances to win though. It was important that the team showed a reaction in the second half."
Meanwhile, goalkeeper Tom Starke claimed he couldn't explain their poor first-half, but did admit that "[Lukas] Podolski released a torpedo from his left foot" for the opener.
Hoffenheim now have 11 points from six Bundesliga matches and take on high-flying Mainz on October 2.