Glasgow Rangers sporting director Ross Wilson was a busy man over the summer as he attempted to improve Giovanni van Bronckhorst's squad in the transfer window.

One area in which he looked to strengthen the club's options was at centre-back as he brought in John Souttar from Hearts and Ben Davies from Liverpool to bolster the ranks after allowing Leon Balogun to depart on a free transfer.

The two new signings are yet to make a significant impact at Ibrox, however, as they have made a combined four appearances in the Premiership so far.

Souttar has not played since the opening day of the season and will now be out of action until after the World Cup after suffering an injury setback, whilst Davies has started the club's last two league matches.

Van Bronckhorst and Wilson will be hoping that both of them turn out to be successes and follow in the footsteps of the other great central defenders who have represented the club in the past.

One centre-back who was a roaring success at Ibrox was Spanish defender Carlos Cuellar, who joined the Light Blues from Spanish side CA Osasuna in the summer of 2007.

The late Walter Smith snapped him up for a fee in the region of £2m and claimed that he was going to be an "excellent" signing as the club were "impressed" by his performances in Europe.

Cuellar lived up to the manager's expectations as he enjoyed a phenomenal debut season in Scotland. The enforcer, who Ally McCoist later described as a "wonderful" player for Rangers, played a whopping 56 matches in all competitions in the 2007/208 campaign.

He featured in 19 times in Europe as the Light Blues made their way to the final of the UEFA Cup - only to lose to Zenit.

The defender also played in the final of the SFA Cup as the Gers beat Queen of the South 3-2 to win the trophy, which capped off an impressive first year in Glasgow for the Spanish centre-back.

His performances did not go unnoticed south of the border and Premier League side Aston Villa swooped in to sign him for a fee in the region of £7.8m in the summer of 2008.

This means that Rangers made a 290% profit on the initial £2m they spent on Cuellar in the space of a year, whilst also getting 56 games out of him and a trophy.

It was a sensational deal all around by the club as Smith struck gold with the defensive machine, both in terms of what he offered on the pitch in his one season at Ibrox and the £5.8m they made from his eventual sale.