Rangers manager Mark Warburton could turn to Philippe Senderos in his search for a fourth centre-back after Joleon Lescott's Ibrox move fell through.
Warburton had expressed optimism on Thursday over the chance of signing Lescott, and the Aston Villa defender subsequently visited Glasgow.
But the move collapsed on Friday morning, with Rangers citing family reasons as the reason Lescott will not be signing for the club.
Villa owner Tony Xia had confirmed his club would pay a portion of Lescott's wages on the final year of his contract, but Sunderland have also been linked with the 34-year-old.
Rangers are still on course to sign Preston striker Joe Garner in a £1.5 million deal, but it is unlikely to be completed before Saturday's Premiership clash with Motherwell.
And they have another option to complete their summer transfer business in Senderos. The 31-year-old former Arsenal defender is a free agent and has been training with the club this week.
Warburton spoke of the former Fulham and Villa player, who had a short spell with Grasshoppers earlier this year, as a serious option on Thursday.
"I can't speak highly enough of Philippe Senderos," Warburton said. "He hadn't been training with a team for a few weeks but his level of fitness is outstanding. His CV is well documented but his level of fitness and the way he has fitted into the group has been first class. He has dealt with training all week effortlessly.
"We have to look at a number of options and I've been very, very impressed by Philippe. Obviously he won't be involved at the weekend. He is going back to Geneva for a couple of days, but we are very pleased with what we have seen.
"But, again, we have to make sure we look at all our options and treat people the right way as well. Players want honest feedback and we will always do that to the players. That leaves us in good stead if we do it that way."
Villa boss Roberto Di Matteo said: "He passed a medical and everything. They didn't agree personal terms so the move has fallen through and he is back with us now.
"It's a headache I've been dealing with from day one, there are a number of players like that [who want to leave]. They have been involved in the group and then I have made a decision on ones who expressed wishes to leave. I will work with the ones who want to be here.
"[Lescott leaving] depends on what solution he will find, one which suits the club and the player."
Whoever comes in to bolster the defence, centre-back Danny Wilson has vowed to keep his place while learning from their experience.
The former Liverpool and Hearts player made 42 appearances last season but he and Rob Kiernan already have added competition from Clint Hill.
"You try and learn from every player, whether they be young or old, in your position or in a different position, you try and take something from every player you can," he said.
"I don't think I'd be doing my job if I wasn't trying to learn from experienced players who are coming in. They have obviously played at a high level throughout their career.
"Any little bit you can take from them is important because I am still relatively young in terms of being a defender, I am only 24.
"So what I can learn will hopefully add to my game and still play my own game at the same time, it can only benefit me.
"If these players come in then I will welcome them. I certainly won't stand aside and just let them take my position, but out there on the training ground I will work as hard as I can, learn from them, and hopefully do enough to get myself in the team on a Saturday.
"Last season we had three centre-halves and this season it is looking like we are going to have four. I did play a lot of games last season so I am confident I will do the same this year."
Meanwhile, Warburton has dismissed Motherwell boss Mark McGhee's assertion that his team should be closer to Rangers than Celtic because of the gap in levels of spending between the Glasgow clubs.
"It's a game of opinions," Warburton said. "That's the beauty of the game, that's why we love it so much. That's Mark's opinion, mine may differ slightly, but we will see after Saturday."
Rangers confirmed some squad news after midfielder Robbie Crawford's contract was cancelled by mutual consent.
The 23-year-old made more than 50 first-team appearances but spent last season on loan at Alloa.
Crawford wrote on Twitter: "After almost 15 years to the day since my first session I'll be leaving @RangersFC.
"Gone through more than most experience in a whole career but had some of the happiest days of my life here.
"Some brilliant people at the club and wish them all the success themselves and the fans deserve. On to the next adventure."