The champions drew 1-1 against Bayern Munich last week in the Bundesliga before their victory over the Italians on Tuesday.
"If we win then we will have had a good phase (until the international break)," Alonso told a press conference. "Then we can prepare for the next block of matches. It was important that we are defending a bit better than we had been last month."
"That is something we need. Without it we are not competitive and we want to be competitive," he said.
Leverkusen, who won a maiden domestic league and Cup double last season without a single defeat, are fourth in the Bundesliga on 10 points from five matches, three behind leaders Bayern.
Alonso said his team would have no problems adapting to arguably weaker opponents after their big-stage matches against Bayern and Milan.
"Every league match is tough and we have learned that this season already," Alonso said. "We expect the same tomorrow. They (visitors Kiel) only have a point but deserve a bit more than what they have at the moment.
"In our heads and our preparation it is only Kiel. We have full respect. They are a good opponent, very flexible in their lineup," he said ahead of his 100th game in charge of the club.
"I expect to see my team to be mature and intelligent. We have to show that we are fully prepared. My team plays with the same motivation in every game so I have no reason to doubt them and we will hopefully show it tomorrow."
