The 55-year-old coach noted that the French side are a strong opponent as they scraped one point from their away game in Group I
The French side took the lead early in the second half through Victor Montano, but a late Juanfran strike rescued a point for the Vicente Calderon outfit.
Atletico were on the back foot for large portions of the game and Manzano admitted that his side had a troublesome match against a stubborn opponent.
"The result is not bad, and within the context of a group of four teams who look even, you have to consider this a good result, specially because of the way it happened," he told AS after the game.
"We suffered Rennes' intensity. They did not give us any room to act. It was either recover the ball or commit a foul. But a draw is a fair result, considering our reaction after suffering the goal."
Manzano went on to praise the French club, saying they are a tough side at the Route de Lorient.
"We know things are very hard in European competitions and Rennes have not lost a match in this stadium in the last four years," he noted.
"Rennes played for the leadership of the league table the other day and they are a team who can be very dangerous."
Atletico are joint leaders in Group I with Udinese, who will welcome the Spanish side in their next Europa League fixture on 20 October.