The forward has struggled in the Premier League so far this season, but netted in a 3-2 win over Stoke City in midweek.
Armstrong, who is 27, scored more goals and provided more assists than anyone in the Football League last term.
He told the Daily Echo: "I think it'll be big for him. Hopefully, it will kick-start his season. He's been really unfortunate because we were playing him as number nine.
"I don't think he's been his most effective for us as a nine. I think he's always been out wide probably, even though he did a great job in the play-offs for us (as a nine).
"I think for us he's been most effective playing wide but he had to play as a nine because Cam Archer came in fairly late and wasn't used to the style of play.
"Paul Onuachu was a bit up in the air. Whilst he was doing that he came out of the team and Tyler Dibling came in on the right and is now one of our top performers.
"It's been really difficult to leave Arma out because I think we're a better team with him in it for sure because of his character and his personality.
"It is also his understanding of what we need and his willingness to run. Tonight will do him the world of good. I thought he was brilliant until he got a bit tired."