Neal, Vale's hero in Saturday's victory at Bradford, let a 30-yard effort from Luke Howell slip through his fingers and over the line as the Daggers took the lead in Tuesday night's League Two clash at Vale Park after 72 minutes.
A fiercely-struck shot from Jennison Myrie-Williams, his fifth goal of the season, brought Vale level just three minutes later.
Adams said: "Chris (Neal) will be disappointed with his error, but he plays in a position where if he does something like that it proves costly. But he's been magnificent all season and has kept us in games, just like he did at Bradford on Saturday. I've got no doubts about his character and I know he will bounce back.
"Overall, I was very disappointed with what was a flat performance. The standards we have met both as a team and individually were just not met. We didn't move the ball quickly enough with players wanting three of four touches when one or two would have done. We also made too many mistakes and late on there was only one team who looked like winning.
"I was delighted we got back on terms so soon after Dagenham scored and that showed a bit of character, but overall I'm not happy. A few players went missing and I'll have to look at that."