New additions Andreas Christensen, Raphinha and Robert Lewandowski were registered just in time got to make their debuts for the Catalan giants.
Raphinha was eager to make an instant impact five minutes gone when he raced onto a ball into the channels by Marc-Andre Ter Stegen, but he had his path to goal thwarted by Stole Dimitrievski.
Barcelona did have the ball in the net after 12 minutes through a cheeky finish from Lewandowski following a ball from Ousmane Dembele, but it was disallowed for offside.
Following the cooling break, the Catalans were close again where Dembele found space out right and cut goal-side to bring a save off Dimitrievski with a low shot.
Rayo came alive on the stroke of halftime after forward Alvaro Garcia charged into the area and cut an angle to rattle the gloves of goalkeeper Ter Stegen.
No substitutes came upon the second half, though Rayo fluffed a golden chance thereafter where Sergio Camello beat Jordi Alba to possession and rounded Ter Stegen before going wide.
Barcelona sprung to life again following the scare and saw Raphinha’s low cross into the area cause uncertainty in the opposition area with Lewandowski lurking around.
Three reinforcements from the Blaugrana arrived on 60 minutes in Frenkie De Jong, Ansu Fati as well as Sergi Roberto with the match keenly balanced.
With Ivorian international Franck Kessie on for his debut, the Catalans continued searching for the opener and as an attempt from Sergio Busquets brought an outstretched save out of Dimitrievski.
Barcelona were denied the winner in the last six minutes after a goal-line clearance denied thwarted Pierre-Emerick Aubameyang’s curling shot before Kessie had one disallowed for offside.
The Catalans finished with ten players in Busquets following a second bookable offence, whilst at the other end, Radamel Falcao saw a close-range goal ruled out for offside as it ended goalless at the Camp Nou.