The visitors are looking to extend their prefect record in pre-season to four matches, while the hosts are preparing for their first game in just under two weeks.
Match preview
For the fourth time in five seasons, Borussia Dortmund had to settle for a runners-up position in the Bundesliga after letting their lead at the summit slip to perennial winners Bayern Munich in heartbreaking fashion on the final day of the 2022-23 season.
Indeed, a 2-2 home draw with Mainz 05 coupled with Bayern's dramatic 2-1 win against Koln helped the reigning champions secure top spot on goal difference and lift their 11th successive German top-flight crown following an enthralling title race during the second half of the campaign.
Dortmund have since dusted themselves down and have made a bright start to pre-season, winning each of their opening three games in Germany by an aggregate score of 12-3, albeit against lower-league opposition.
A thumping 7-0 win over fifth-tier outfit Westfalia Rhynern was followed by a 3-2 victory against fourth-tier side Rot-Weiss Oberhausen as week later, while their most recent success came against another fourth-tier team in Rot-Weiss Erfurt, with two goals in the final 10 minutes from Thorgan Hazard and Marius Wolf securing a 2-1 comeback win last Saturday.
Head coach Edin Terzic acknowledged that his side 'lacked rhythm' in their last outing and he would have liked to have seen his side "perform more confidently", but the 40-year-old still managed to take some positives from the victory.
Dortmund will begin their tour of the USA with Friday's favourable-looking clash against San Diego Loyal before preparing for a tougher run of fixtures versus Manchester United, Chelsea and Ajax, facing the latter on home soil in their final warm-up match on August 6.
As for San Diego Loyal, they are currently two-thirds of the way through their USL Championship campaign, although they will have had 12 days to prepare for Friday's contest.
Indeed, Loyal's last outing was on July 15 when they secured an impressive 5-0 away triumph over Colorado Springs, six days after beating Hartford Athletic by a 2-0 scoreline.
Managed by Nate Miller, who took the reins from American soccer icon Landon Donovan in December 2022, San Diego Loyal are competing in just their fourth season since they were founded in 2019, an they currently sit fifth in the USL Championship Western Conference, only five points behind Sacramento Republic at the summit.
The California-based club are now preparing for six successive home matches in all competitions including their first-ever game against European opposition in Borussia Dortmund, who will be welcomed with open arms to the 6,000-seated Snapdragon Stadium on Friday.
San Diego Loyal form (all competitions):
Borussia Dortmund friendly form:
Team News
Borussia Dortmund centre-back Niklas Sule missed the last friendly match due to a gastrointestinal infection and will be assessed ahead of kickoff, as will USA international Giovanni Reyna and English teenager Jamie Bynoe-Gittens who are both making positive strides in their return to full fitness.
Terzic has confirmed that Karim Adeyemi is expected to return on Friday after missing the win over Rot-Weiss Erfurt and he could battle with Wolf, Hazard, Donyell Malen and Julien Duranville for a place on the flanks.
Summer signings Ramy Bensebaini and Felix Nmecha both made their debuts last weekend and are set to be involved again in California, while BVB's newest recruit Marcel Sabitzer - who joined permanently from Bayern on Monday - is also in contention to feature.
As for San Diego Loyal, Miller is expected to field a strong lineup which will likely include top scorer Evan Conway, who has found the net nine times so far this season including three strikes in his last three appearances.
Adrien Perez, Blake Bodily, Tumi Moshobane and Elliot Collier were all on the scoresheet in the comfortable victory over Colorado and they will be pushing to start against Dortmund.
San Diego Loyal possible starting lineup:
Koke; Riley, Stoneman, E. Martin; Perez, Corona, C. Martin, Adams, Bodily; Moshobane, Conway
Borussia Dortmund possible starting lineup:
Kobal; Meunier, Hummels, Schlotterbeck, Bensebaini; Ozcan, Nmecha; Adeyemi, Reus, Hazard; Haller
We say: San Diego Loyal 0-3 Borussia Dortmund
Friday's contest will be a special occasion for San Diego Loyal as they take on a club with the European pedigree of Borussia Dortmund, who will be regarded as firm favourites to come out on top here.
Indeed, should Terzic name several star names in his lineup, the Germans should have few problems coming away with a comfortable victory in California.