The new Royals manager oversaw a disappointing defeat to League Two outfit Sutton United in his first match in charge, while Southampton drew with Turkish side Goztepe last time out.
Match preview
Reading are preparing for life in League One following relegation from the Championship last term, as the Royals finished five points inside the drop zone after receiving a six-point deduction for breaching an EFL business plan.
The Berkshire club parted ways with manager Paul Ince in April, but interim boss Noel Hunt failed to turn things around at the Madejski Stadium, meaning that Reading will play in the third tier for the first time since 2002.
Given that Reading failed to win any of their final 13 matches in 2022-23 - recording six draws and seven losses in the process - they can have very few complaints about last season's relegation.
The Royals started their pre-season preparations by suffering a 1-0 home defeat to AFC Wimbledon, before Ruben Selles oversaw a 2-0 loss at Sutton United in the first game of his tenure.
Funnily enough, Selles' second match as Reading manager is against the club that he took down two months ago, so the Spaniard will be eager to get one over on his former side and pick up his first win in his new role.
Selles' replacement, Russell Martin, has also failed to taste victory in his new role, as the former Swansea City boss has overseen a draw and a loss since arriving on the south coast.
Following a 2-0 defeat against Portuguese giants Benfica, the Saints played out a 1-1 draw with Turkey's Goztepe last weekend, with Carlos Alcaraz equalising for his side after a rare penalty miss from James Ward-Prowse.
It is no secret that Southampton endured a 2022-23 campaign to forget, recording six wins, seven draws and 25 losses to finish six points adrift at the foot of the Premier League table.
As a result, the Saints are preparing for life in the second tier for the first time since 2011-12, having enjoyed 11 consecutive seasons in the top flight, with four top-eight finishes and a Europa League appearance coming along the way.
Naturally, Southampton are among the favorites for Championship promotion in 2023-24, but Martin and his players will know that returning to the Premier League at the first time of asking will not be easy.
Reading friendly form:
Reading form (all competitions):
L
D
D
L
D
L
Southampton friendly form:
L
D
Southampton form (all competitions):
L
L
L
D
L
D
Team News
Reading have been forced to part ways with a number of important players following relegation, with George Puscas joining Italian side Genoa and Tom Ince leaving for Watford.
The Royals have signed Cambridge United duo Sam Smith and Harvey Knibbs, but Selles will be eager to sign more players ahead of the new campaign, as his squad is worryingly thin.
Southampton have also been busy in the transfer market this summer, signing Shea Charles from Manchester City and Ryan Manning from Martin's former club Swansea.
Mislav Orsic, Mateusz Lis and Dan Nlundulu have moved elsewhere, while Theo Walcott and Mohamed Elyounoussi have been released, with Willy Caballero hanging up his gloves.
Big-name players such as James Ward-Prowse, Kyle Walker-Peters and Che Adams started last weekend's draw with Goztepe, although question marks remain over their future at the club.
Reading possible starting lineup:
Bouzanis; Abbey, Guiness-Walker, Holmes, McIntyre; Abrefa, Azeez, Ehibhatiomhan, Hutchinson; Knibbs, Abdul-Salam
Southampton possible starting lineup:
Bazunu; Livramento, Lyanco, Stephens, Walker-Peters; Smallbone, Ward-Prowse, Doyle; Tellas, Adams, Armstrong
We say: Reading 0-3 Southampton
We expect Ruben Selles to endure a difficult afternoon against his former club, as the Saints look set to cruise to comfortable victory against Reading.