Sherwood made it four wins from a possible five in the Barclays Premier League on Saturday when his Tottenham team beat Crystal Palace 2-0 at White Hart Lane.
Christian Eriksen put Spurs ahead, but it was Toronto-bound Defoe who ultimately settled the match, firing home from inside the Palace box 15 minutes after his introduction as a second-half substitute.
Spurs confirmed on Friday that Defoe will leave White Hart Lane for Toronto FC at the end of February.
The 31-year-old, for whom Toronto will pay over £8million, has been a peripheral figure at Tottenham this season, but Dembele is still not looking forward to seeing the player depart.
"For us he's very important. I think everyone knows his quality and of course we will miss him, for sure," the midfielder said.
"It was nice for him to score, though. We are happy for him."
Spurs looked unlikely to claim what turned out to be their fifth home win of the campaign after a poor showing in the first half.
Palace should have gone ahead in the eighth minute when Dembele clattered into Marouane Chamakh inside the Spurs box.
Referee Michael Oliver pointed to the spot, but Jason Puncheon failed miserably from 12 yards, blasting his effort high and wide of Hugo Lloris' goal.
Palace continued to dominate for the remainder of the first half, and they were unlucky to come away from the game with nothing.
Dembele admits Spurs need to up their game in the coming weeks against better opposition if they are to maintain their push for Champions League qualification.
The Belgian said: "Against other teams we would have lost the game.
"It's difficult to know why we started so slow. We were not good in the first half.
"We played sloppy balls. We weren't concentrated. In the dressing room the gaffer told us (at half-time) we needed to concentrate more and work harder and I think we did."
Still, with Spurs having dropped just two points from their five league games under Sherwood, Dembele thinks Tottenham are looking good in their quest for Champions League football.
This week has been the first time that Sherwood has had five days to get his ideas across to his players because of the hectic nature of the festive period.
Dembele has been impressed with the 44-year-old, whose only previous experience in management came with Tottenham's development squad.
"He gives us a lot of confidence," Dembele said of Sherwood.
"Everyone likes this.
"We didn't have a lot of time to train too much together because of the amount of games but you can see already that our style is good.
"He tells us to attack more but not with too much risk.
"But we still need to do better first half and if we do that then we can do some great things in the second half of the season."
While Tottenham's win kept them in touch with the hunt for a top-four place, Palace slumped to the foot of the Barclays Premier League table.
Results and performances have improved under Tony Pulis, though, so Yannick Bolasie is confident the south London club will avoid the drop.
"We have been at the bottom of the table before and the boys are not discouraged," the winger said.
"Our next game is at home against Stoke - the gaffer's former team - so I am sure he will be fired up for it and the boys will be as well."
Bolasie also backed Puncheon to get over his terrible penalty miss.
"Jason is all right," Bolasie added.
"He doesn't really get down. I think he will be quickly back to himself again."
Source : PA
Source: PA