Despite Sainz himself previously admitting he understood the team's decision to bring Hamilton in, some have questioned whether the team are making an upgrade.
This rhetoric was louder when Hamilton struggled earlier in the campaign, though his recent resurgence has quietened dissenters.
Vasseur hails seven-time champion
The Brit endured a miserable opening quarter in 2024, having been consistently outperformed by team-mate George Russell in his efforts to challenge the top of the order.
Sainz on the other hand, was a regular feature on the podium, and had already celebrated a victory at the Australian Grand Prix in what was an impressive start to the season.
However, Hamilton has closed the gap to his Spanish counterpart in recent weeks - aided by wins at Silverstone and Spa - and demonstrated why the 39-year-old is widely regarded as one of the best drivers in the sport's history.
The former McLaren star will hope to finish with a flourish at Mercedes before embarking on his new challenge at Ferrari, as he aims to win a historic eighth drivers' title, something Vasseur believes he is capable of doing.
Speaking to Sky Italia after Hamilton's controversial victory in Belgium, the Ferrari team principal highlighted that despite some previously claiming the 105-time race winner was past his best, he still has plenty to offer.
“We certainly know the positive aspects of Lewis’ arrival, such as his great experience,” Vasseur said.
“Everyone since the beginning of the season has said that Russell is faster than him, but at the moment he is the one who has brought more points to Mercedes.
"So in terms of efficiency I think he is a good point of reference.”