Andy Hessenthaler hopes Dover’s shock weekend loss serves as “a kick up the backside” for his players.
Whites lost 1-0 to Larkfield & New Hythe, who play in Southern Counties East League Division 1 - four leagues below.
Dover’s boss admits it was a game he expected his side to win, but says he learnt plenty from the fixture.
“[It’s] not good to be honest,” Hessenthaler reflected.
“I will be honest, the pitch was not particularly good. It was going to be the youth section that was going to use it [the friendly] but we didn’t have a game ourselves.
“We expected to go and win the game - but we didn’t. Not being disrespectful to them, but we should be winning those games.
“But if you win the game 5-0 or 6-0, how much do you learn from it? I learnt a lot on Saturday about the group.
“It’s a bit of a kick up the backside. It’s a little bit concerning but we won’t get too carried away.
“I have been at clubs where we have won every friendly, then you lose the first two or three games of the season after it.”
This summer, as Whites prepare for life in National League South, changes have been made and Hessenthaler concedes it may be taking a little bit of time for the squad to gel.
He said: “It’s taking a little bit of time but we will get there. On paper, we look a good side, but we have to gel it all together.
“The problem with pre-season is you are using so many players. Once the season starts - yes, you will make changes during games and pick up injuries - but you don’t get trialists coming in and out. I do get frustrated with pre-season.
“But it’s important we get together now and use the rest of pre-season to be ready for August 6.”
Dover, who started pre-season with a win over Gillingham, have also suffered losses to Deal (1-0), Margate (2-0) and Brighton under-23s (4-1).
They are due to visit Steve Lovell’s Ramsgate tonight (7.30pm kick-off) and end their run of warm-up fixtures at Isthmian Premier Folkestone this Saturday, ahead of their season opener at Worthing on August 6.
Hessenthaler explained: “We want to get a bit of momentum and a bit of confidence. It’s always nice to take that into the season.
“We need a performance against Ramsgate and then against Folkestone at the weekend.
“You don’t want to win all the friendlies really - because everyone then gets carried away - but the last couple of games have not been good enough, especially Saturday.”
Hessenthaler is relatively happy with his squad, although didn’t rule out further additions this summer.
“[Midfielder] George Wilkinson cannot play the first game, he will be suspended,” he said.
“I think we are always looking out for players. If someone can improve us, I’m sure the chairman [Jim Parmenter] will dig deep. The balance is good.
“Not many players have played 90 minutes, we will need to get some 90 minutes so players are up to speed and ready for the season.”
Striker Alfie Pavey scored in their loss to Brighton last Wednesday.