The Andalucian club and Zaragoza both reported infections the day after Real Madrid revealed Mariano had tested positive
The player was tested on Sunday along with coaching staff and the rest of the first-team squad, before the results were returned on Monday.
Gudelj, who chose to waive anonymity in order to send a message to fans on Wednesday, is asymptomatic and self-isolating at home, though the club immediately suspended training sessions.
“Good afternoon everybody, after confirming my positive Covid-19 test I want to tell you all that I am perfectly fine, I have no symptoms,” the former Ajax midfielder explained in a video released on his official Twitter page.
“I hope to be back with my team-mates soon and help the club reach its goals at the end of this season.
“Thanks for all your messages of support, we are still here training and we’ll see you soon.”
Two further tests have since been carried out on the rest of the squad and the coaching staff.
While the first batch of tests all came back negative, Sevilla do not expect the results of the second round to be known until Thursday.
— Sevilla FC (@SevillaFC_ENG) July 29, 2020
Should there be no further positive results among the side’s squad and employees, Sevilla plan to return to individual training – with “all the applicable measures” in place – on Thursday.
The Andalucians are one of a string of sides in Spain who have seen their plans disrupted by a fresh outbreak of the virus, which has led the United Kingdom to issue travel restrictions in recent days.
Real Madrid confirmed on Tuesday that forward Mariano was suffering from the virus ahead of their trip to the Etihad Stadium to take on Manchester City in the Champions League, while Segunda Division side Zaragoza have also seen an unnamed player return positive in testing prior to participating in the upcoming promotion play-offs.