Owen, who ended last season with 12 goals in his final 14 appearances, started the road to the new campaign with two well-taken goals in the Reds comfortable 3-1 victory over Cologne.
Houllier said: "Since Michael and Steven Gerrard broke into the side I don't remember them ever being able to take part in a full pre-season with us, either because of injury or internationals.
"There were always some training sessions they had to miss. Last year Michael came back from the World Cup with an injury, you will remember. This time it is different.
"Michael and Steven have not missed a training session. I think Michael has shown a great improvement in all aspects of his game - but it is probably the physicality of his football which is developing the most.
"He looks a lot stronger and that is the area where he has been working hardest. Even last night the way he was tackling back and helping to close down opponents was brilliant.
"His passing was excellent and of course he scored two goals. I said six months ago I believed Michael would be awesome this season and I still believe that is going to be the case.
"We have to be very careful because we are just starting our pre season, but the signs are very good for him."