Even before pre-season testing started in Bahrain there were positive rumours about Aston's aero numbers.
While it is still hard to draw conclusions from the timesheets as testing rolls into the third and final day, rival drivers and teams have seen enough from Alonso's long runs and his AMR23's compliant behaviour to single Aston out as one of the teams to watch this season.
"It's clear Aston Martin did a step," said Alfa Romeo's Zhou, who shared the track with the two-time world champion for all of Friday.
"Alonso seems to be very competitive over the two days, both conditions. I think he will be one of the top guys in midfield battle."
Zhou topped Friday's timetable, albeit on Pirelli's softest C5 tyres, but thinks Alfa won't be too far off either after it enjoyed a productive and trouble-free pre-season.
"It seems like we both made a step and over the two days they seem to be a little bit faster, but we're close.
"I feel like there's still areas I can improve and there will be another tight battle."
When Kevin Magnussen was asked if anyone caught his attention, the Haas driver also singled out Aston.
"I think Aston Martin looks fast. They seem to constantly be doing good long runs," he said.
"And when they try to put a lap time they seem to do it as well. So I think they look like they've done a big step. But again, who knows."
Alpine's Esteban Ocon agreed with that assessment, but pointed out that there are still too many variables to get a reliable picture.
"I think it's early days to really give conclusion," he cautioned. "With those cars, it's so easy to go from five seconds slower to five seconds quicker in one go, so... it's difficult to exactly tell, the fuel loads, the energy management and what engine mode you run.
"They look for sure competitive at the moment, but the Williams also look competitive. I think it's gonna be a close fight, like it always is."
Aston Martin disappointingly finished seventh in the 2022 season but the Lawrence Stroll-owned team has gone on a large recruiting spree, spearheaded by the arrival of former Red Bull aero chief Dan Fallows as its new technical director.
Alonso is undertaking the bulk of Aston's testing this week, with Lance Stroll ruled out after sustaining a wrist injury in a bike accident.
While it is still unknown if Stroll will be fit in time for next weekend's season opener, reserve driver Felipe Drugovich has deputised for the Canadian in the Bahrain test.
