Giovanni van Bronckhorst revealed the quest for Champions League football helped him decide to leave Alfredo Morelos out of the Rangers squad to face PSV Eindhoven on Wednesday night.
The Gers boss omitted the Colombia striker for the second-leg tie of the play-off in Holland due to fitness levels and other concerns, including attitude.
Morelos, 26, who recently returned to the squad following a long spell on the sidelines following a thigh injury, was sent off 13 minutes after coming on as substitute in the 2-2 draw with Hibernian at Easter Road on Saturday.
However, Van Bronckhorst insists it was "something that was building up" and was "a signal I had to make to Morelos and also to my team" as he spoke ahead of the game at the Philips stadium, where the game will start with the sides tied 2-2 from the first leg at Ibrox.
Rangers look to take the final step towards the Champions League for the first time since the 2010-11 season.
"It is always the case that I bring players with me who are ready to play and for me that was the moment I didn't include Morelos," said Van Bronckhorst, who confirmed Glen Kamara was back in the squad but Kemar Roofe, Ben Davies and John Souttar remain out.
"As a person it was a hard decision. As a manager it was an easy one because we are here to represent our club and to get into the Champions League tomorrow evening.
"I made the decision myself. Of course we have a leader group and I always keep contact with them.
"We will wait and see what happens (going forward). The biggest factor in that is Alfredo himself. We will have to see how the coming days and weeks will go.
"He has to show me he wants to play for Rangers. I know he wants to play but to play for Rangers you have to have a certain level, mentally and physically he is not ready to play."
Van Bronckhorst will go again with Antonio Colak as his main attacker in the Netherlands.
The Croatia striker has scored four goals in his last five games and has kept Morelos on the bench.
The Dutchman said: "Antonio has done really well. He has had a positive impact on the team with his performances, and of course with his goals because we need goals to win games."
On his Instagram account, Morelos posted a cryptic message in Spanish on an image which translated to: "The best warrior is not the one who always triumphs but the one who returns without fear to battle.
Morelos captioned the post with the words "miedo a dios" which translates to "fear of God".
PSV manager Ruud van Nistelrooy believes his side can take advantage of their free weekend to get past Rangers
While last season's Europa League finalists had to play at Easter Road on Saturday, PSV’s fixture against Volendam was postponed to allow the Dutch side to prepare fully for the second leg of their Champions League play-off at the Philips Stadion on Wednesday night.
Quoted on the PSV website, he said: "We showed ourselves very well last week. Everyone knew beforehand that the duel at Ibrox would be tough.
"Rangers lived up to those expectations. In addition to the support from the stands, which leads to a lot of energy on the field, Rangers play smart, modern football.
"Rangers did a great job reaching the Europa League final last season and much of that team is still intact.
"In addition, the team has strengthened itself with some newcomers.
"A draw is then a good result. Of course the competition has been evaluated by us.
"Because we didn’t play last weekend, we were able to focus on points that deserve extra attention after analysis. I hope and expect that we will take advantage of that.
"It is a dream for us to play in the Champions League. We will do everything we can to make it to the main tournament."
PSV’s Brazilian centre-back Andre Ramalho is glad the Dutch authorities postponed the Volendam fixture and believes it could work in their favour, especially if the tie against a side which impressed him at Ibrox goes to extra time.
He said: "Rangers play with a lot of intensity. We experienced that last week. (On Wednesday) we will play against a team that fights for every metre and is physically very strong.
"Our response to that was good. I think the 2-2 was a fair reflection of the game. I appreciate that the KNVB moved last weekend’s match.
"A lot depends on the game we play with Rangers. Every little bit can help us to achieve a good result.
"The support of our crowd, good preparation and fitness can play a role, especially if the game is not decided after 90 minutes."
Watch Benfica v Dynamo Kiev in the Champions League play-off round second leg on RTÉ2 and RTE Player on Tuesday from 7.45pm
