The Catalan giants have won all three of their summer matches thus far, while Salzburg have started their 2021-22 campaign in style with back-to-back wins.
The biggest issue concerning Barcelona with a fortnight to go until the new La Liga campaign begins is the future of star man Lionel Messi, who still remains a free agent.
Depay has settled in well to his new surroundings, scoring in his first two appearances for Barca in their 3-1 win against Girona and 3-0 victory against Stuttgart.
Koeman's charges have also seen off Gimnastic 4-0 during pre-season, so results are certainly not a problem at this stage.
Barca have based themselves in Germany for this stage of their pre-season campaign, though they will cross the border into Austria on Wednesday for this friendly with Salzburg.
This will be the first ever meeting between the sides, and it is also the first time Barcelona have played a match of any sort in Austria since 1993.
Salzburg should be a lot fitter than their opponents, having already played a couple of matches in the Austrian Bundesliga this season.
The Red Bulls beat Strum Graz 3-1 in their first competitive game of 2021-22 and crushed SV Ried 7-1 on Sunday to move top of the table even at this early stage.
Matthias Jaissle's men are favourites to retain their title for a ninth campaign in a row, and they enter this match with just two defeats in 22 competitive and friendly games.
Barcelona are expected to agree a new long-term deal with Messi, but the superstar forward remains absent for the time being, as does fellow Argentina international Aguero.
Garcia is away on Olympics duty with Spain, while academy graduate Alex Collado is another absentee for this friendly as he has been given permission to seek a transfer.
As for Salzburg, recently-appointed boss Jaissle's main focus will be on next weekend's league clash with Austria Vienna.
However, the hosts are still expected to name a very strong lineup on Wednesday as they look to get one over on Barcelona in this first ever meeting between the sides.
Karim Adeyemi has been linked with a number of heavyweight clubs this summer and has scored three goals in Salzburg's last two games, making him one to watch here.
Salzburg possible starting lineup:
Kohn; Kristensen, Solet, Wober, Ulmer; Sucic, Junuzovic, Seiwald; Aaronson; Sesko, Adeyemi
Barcelona possible starting lineup:
Neto; Roberto, Pique, Araujo, Dest; Puig, Busquets, Gavi; Demir, Manaj, Depay
We say: Salzburg 2-2 Barcelona
Barcelona have made a positive start to pre-season and have just one more friendly - against Juventus at Camp Nou next weekend - before beginning their La Liga campaign.
Koeman will be eager to keep the momentum going into that season-opening fixture with Real Sociedad, but this is undoubtedly the toughest opponent his side have faced yet.
That is due to Salzburg having already started their 2021-22 campaign, doing so in style by scoring 10 goals in their opening two wins, and we can see them claiming a draw here.