The team trail 2-0 to Belgian outfit Royale Union Saint-Gilloise from the first-leg.
Kent missed out after picking up an ankle injury in the opening-day win over Livingston.
“Ryan for today, it was too short,” Van Bronckhorst said.
"We are working hard to get him ready for Tuesday. Hopefully we will manage to do so.”
Van Bronckhorst saw Alfredo Morelos return to action as a second-half substitution, the Colombian netting the second in a 2-0 win over Kilmarnock.
The striker last played for Rangers in March and will be sure to feature on Tuesday but Van Bronckhorst was coy on whether he would start.
“It is his first minutes for Rangers after five months,” he said. “If you think about it, it is a really long time and almost half a year.
"It was good to have him in the squad. You can see what he brings, not only to the squad but also the way the fans treated him when he came on. That is also what you have when he plays and he is always capable of scoring goals.
"For him, I think these first minutes of the season and after five months were very important and I am sure he will only get stronger with each game that he is going to be involved.”
With 18 shots from 73 per cent possession, Rangers only created two big chances.
The team will have to score at least two against Union SG and Van Bronckhorst is confident an increased threat in the final third will materialise.
“I think we will improve in those areas, for sure,” he said. “We have many new players in and it is also adjusting to the new system for them and different teammates.
"In the first five minutes we came through their defence quite a lot and were a bit unlucky not to score earlier.
"As long as we keep working hard in training and keep trying to create as many chances as we can, I think we will improve with each game we play.”