Damon Hill believes Ferrari have an inconsistency problem which makes it unclear as to how strong they will be from race to race.
Carlos Sainz and Charles Leclerc had very strong race pace at the two Austrian rouds, following a nightmare at Paul Ricard when they went backwards. Leclerc has also had two pole positions this season but failed to make Q3 at the Austrian GP.
"I think, as Carlos has said, they don't know what to expect with Ferrari," Hill told the F1 Nations podcast. "They turn up at a circuit one minute it's great, next minute it's not, qualifies well, and then races badly. So Ferrari are all over the place, up and down.
"But they should have the potential to be good at Silverstone and they have been strong in the past at Silverstone."
Hill thinks Ferrari's main rivals, McLaren, are the team to watch after Lando Norris' first ever F1 front row start last time out in Austria. Norris is racing on home soil and could spring another surprise by beating Red Bull or Mercedes.
"I think that McLaren are on the march," said Hill. "They are definitely creeping further and further, closer and closer to the guys at the front end. I mean, they very nearly had pole position in the Austrian Grand Prix.
"Lando has been qualifying brilliantly so he has a brilliant opportunity in the Friday qualifying. They must be jumping up and down with excitement."