The former England captain declared last week that, at the conclusion of the current season, he will step down after 11 years.
Surrey has won the County Championship three times under Stewart’s leadership and is looking for a third straight victory this year.
Stewart played for Surrey for 22 years, scoring 40,936 runs in 951 matches, including 67 hundreds.
Batty told news Radio London, “He’s been the best director of cricket, just like he was the best player when he played.”
“He’s driven by excellence and he’s done that again in a role off the field – we can’t replace that.”
With the exception of batter Dan Lawrence from Essex, Surrey’s roster remains essentially unchanged from the previous campaign.
As Surrey looks to win a third straight crown, former England spinner Batty stated that the team’s mindset “has to be about winning things”.
“We’ve discussed winning the T20 Blast, the 50-over [championship], and the County Championship, but it all comes down to the method by which we’re going to accomplish that.
“Knowing Alec isn’t going to be around in a full-time capacity next year – for those that are driven by the emotional side it’s a lovely add-on, for those who aren’t it doesn’t matter, it’s still going to be win – this group is driven for success.”