By FOX Sports Staff
The Spanish side looked the better team for much of the game and had a one-man advantage after Rubin's Cristian Ansaldi was sent off for collecting two yellow cards early in the second half.
But they lost a man of their own a minute later when Michel was shown a straight red and could not score a vital home goal at the Estadio Ciudad de Valencia. It means that the tie will only be decided next Thursday when Levante pay a visit to chilly Russia.
"We deserved a better result, but our mistakes will motivate us for the second leg," Martinez commented after the game.
"Maybe, an away goal in Russia can complicate things for the opponent."
Speaking on the artificial surface at Rubin's stadium, Martinez added: "The surface is different and we are not used to it. It is not very wide and they have good support."
Furthermore, he dismissed suggestions that he could have done something to prevent Michel's sending-off.
"I had no time - after the sending-off of the Rubin player - to make a change. Everything happened so fast.
"I don't know if it was a violent challenge or not, but he slipped.
"Michel is a talented player and will bounce back."
Levante remain the only Spanish side in the competition after the elimination of Athletic Bilbao and Atletico Madrid in the previous rounds.