Earlier this month, it was revealed that Foreman will be bowing out from his role as Derek Branning in a big Christmas storyline. He has been appearing in the part for nearly a year.
Witts, who plays Joey Branning, told Inside Soap of the news: "I'm sad, all my early memories of being in EastEnders are with Jamie. Jamie's been so generous with his time and really looked after me.
"But I doubt he'll be sad for long because I know he'll move on to other great jobs."
Asked how Joey will react to his dad's exit, he replied: "You'd think he'd shrug it off. But Joey is all over the place, so his reaction may be surprising."
In the meantime, viewers can expect Joey's relationship with his cousin Lauren (Jacqueline Jossa) to hot up next week as they share a kiss. The pair are currently falling for each other in a surprising new storyline.
Offering his take on the plot, Witts said: "If they had grown up together or played together as kids, then I could understand people thinking it's creepy or weird. But they've met as adults and it's only because they've been told they are cousins that they even know they're related.
"With the Brannings being the Brannings, it's bound to kick off. They won't be very happy about this at all."
EastEnders continues tonight (October 23) at 7.30pm on BBC One.