The two big players in Scotland's title race sometimes like to have a free agent ace up their sleeve to varying degrees of success.
We've seen Freddie Ljungberg and Carlton Cole pitch up at Celtic outside of transfer windows, seemingly losing all semblance of talent after passing Hadrian's Wall.
But a nifty free transfer at Rangers was often Walter Smith's calling card and they ranged from the outlandishly successful (David Weir) to the forgettable (Salim Kerkar).
Now in the closest title race since the sorely missed Ibrox legend was in charge down Edmiston Drive, might a post-January deal help get the champions over the line?
The after effects of Covid-19 and teams coming to the realisation that getting an exorbitant earner off their wage bill at any cost has given the free agent something of a renaissance.
No longer can the term be looked down upon when some of the game's biggest stars are being cut adrift or moving on for free of their own volition.
Ange Postecoglou seems happy with his business but if Gio van Bronckhorst fancies one last body in, he's got plenty of options in these five free agents.
Mateo Musacchio
Hearts fans were left snickering when they witnessed Celtic smash three goals past Rangers on derby night last week.
"Could have done with John Souttar, lads," was the line from Gorgie but the laughs diminished when the same was true for the sorry maroon defence that let five past them on Sunday afternoon.
Rangers might not have Souttar yet but they could land a stop-gap that, as far as stop-gaps go, isn't half bad.
Argentine defender Musacchio has 150 La Liga appearances for Villarreal in the bank and about half as many in Serie A for AC Milan and latterly Lazio.
He's been without a club so far this season and if he could prove he's in the clear after ankle surgery the 31-year-old would provide a solid option in addition to Connor Goldson, Leon Balogun and Calvin Bassey, who looked far more comfortable at left-back against the Jambos.
Filip Helander's fitness clearly cannot be relied upon at the moment, two months on from when he was originally slated to return, while Jack Simpson's days appear numbered.
Frank Castaneda
One from left-field now and a man who can come in and instantly contribute.
You'll find most of the names on this list need a little bit of rehabilitation.
Usually it's a set of extraordinary circumstances or serious injury that leaves you without a club after the January window.
But Colombian frontman Castaneda has only just left Sheriff Tiraspol after his contract expired in January. He is fit and ready for action.
Do I hear sneering at the Moldovan champions up the back? At least they were in the Champions League this season - and took down Real Madrid at the Bernabeu, no less.
Okay, it would be a step up in expectation and week-to-week quality but he's coming from a club that would absolutely go toe-to-toe with either Celtic or Rangers in a qualifier.
Capable of playing out wide or centrally and with plenty of good years left at 27, Castaneda has 42 goals in 75 games for Sheriff and his strike rate with Senica in the Czech Fortuna Liga was equally decent.
Clearly, Alfredo Morelos needs a bit of help up top.
Cedric Itten looks incapable of contributing while Kemar Roofe is a great option but his fitness is patchy at best. A move for another goalscoring Colombian for no outlay makes perfect sense.
Clement Grenier
Last seen at Stade Rennes where he played against Celtic, midfielder Grenier has been training with the another former club Lyon to prove he's serious about getting back into the game.
And in December Ligue 1 side ESTAC Troyes showed an interest but that didn't materialise into a move.
Once named in the France squad for the 2014 World Cup, his big moment passed him by due to an injury six days before the opening match.
He never played for Les Bleus again and now at 31 there's a sense of unrealised potential.
But that shouldn't put off either of Glasgow's big pairing to land a man with some serious continental experience.
His lack of matches - he was without a club for the entirety of last season - is a worry but if such a gamble paid off it would be a masterstroke.
Laurent Koscielny
Let's stay with France and Van Bronckhorst can look across the city to take a leaf out of the Brendan Rodgers book for this one.
It was Kolo Toure the Antrim gaffer snapped up back in summer 2016 who played a part in Liverpool's title near miss two years earlier.
And while he didn't play much having a voice of experience at the very highest level is said to have been vital that season.
Former Arsenal defender Koscielny has left Bordeaux in rather acrimonious circumstances and while he's now 36 the centre-back could still offer plenty in the Ibrox dressing room.
One of the benefits of the Toure transfer was that when he hung up his boots at the end of the season it was Rodgers and Celtic he immediately turned to for a new career in coaching.
Van Bronckhorst could repeat that feat with some outside the box thinking and on the pitch, as already noted, Rangers are in need of another centre-back.
Jack Wilshere
Okay, this one has been done to death.
But it is quite incredible how Jack Wilshere still is without a club despite serious efforts to get himself fit.
Quite what this former boy wonder of Arsenal and England needs to do to find a club is beyond most of us mere onlookers.
He's been training with Mikel Arteta's side for months now - travelling out for their winter camp in Dubai and back again to London Colney - and they're not even the first club to invite him in for sessions.
FC Como over in Italy was the backdrop in August when he tried hard to land a deal in Serie B but that also fell through.
All throughout, links to Rangers under Steven Gerrard's leadership remained strong but nothing ever quite came to pass.
After signing his old Emirates midfield mate Aaron Ramsey on deadline day, however, the stage is set.
And he'd surely be happy to let Van Bronckhorst have a look up at him up at Auchenhowie first.
