Myles Peart-Harris arrived as Boro's first signing of the summer last week and he's set to be joined by Kyle Joseph, with a new deal agreed with Hull City on Wednesday evening after a move for the forward initially stalled last week.
Joseph is expected to be confirmed as a Boro player before the week is out, which will be another big boost as the recruitment team look to freshen up and reshape the squad after last season's Wembley heartbreak.
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Boro have lost influential Teessiders Hayden Hackney and Dael Fry but Hellberg says he's armed with plenty of experience of losing key players and is confident replacements will be found for those who have moved on.
Boro will sign at least one No. 9 this summer and more attacking reinforcements are still wanted.At least two midfielders will arrive, while Boro will also prioritise the capture of a left- back and, after Fry's exit, a centre-half. A senior goalkeeper is also on Boro's wishlist.
And Hellberg believes everything will come together.
"I'm very hopeful," he told the Northern Echo from Boro's training camp in Portugal.
"For me, we are working very very hard here and very hard to sign players that suit the way we want to play.
"We need to take a step to make it a bigger squad. Our squad wasn't deep enough last season, everyone saw that. I'm not hiding from that, I think that's common ground for everyone.
"But that doesn't mean you have to sign 11 players, that can also be giving the young kids the preparation to get there.
"Then adding pace. I think could see that in the final. The worst thing that happened to us was Tommy [Conway] didn't play.
"If there was one player you wouldn't take away for the final, it was Tommy. We need to have more than one player with that pace. I hope and I think the squad will be stronger as a unit when we start."
In an ideal world, Hellberg admits Boro would have more reinforcements through the door by now.
But he knows it doesn't work like that, and he says the lack of depth in the squad as things stand presents opportunities for youngsters and fringe figures.
He said: "Of course as a coach, I know this won't happen, but you'd love six or seven new players here straight away. But that rarely happens.
"And sometimes they come a little bit later and that's opened up opportunities for other players who might not have had that opportunity.
"So I get to see five or six really good young players that I get to see training with us and give them the possibility to take that chance. It's the same for players coming back from loans. Good things can come of it.
"Of course we would like everyone standing here ready to go but that's not the way it is."
Hackney's exit was anticipated this summer and the midfielder - last season's Championship Player of the Season - completed his move to Everton last week.
But Fry's exit to join Birmingham came as something of a surprise.
Both Fry and Hackney starred last season, while Boro also have to replace Alan Browne and Matt Targett, who left the Riverside after their season-long loan moves came to an end.
Hellberg said: "We have lost four of the players who played almost every game in Dael, Browney, Matt, and Hayden.
"Hayden was the best player in the league. Dael was unbelievable at the end of the season. He moved forward during the season. He was unbelievable against Southampton and in the final.
"They are very good players but now they're not here. You work with what you have and what we're trying to get in.
"Even if you lose a good player, positive things can come from that. The ones that come in might not be as good at certain things but maybe give us something else, or maybe you get two players.
"At Hammarby, we sold a lot of players but we still developed the team all the time. That's what we're trying to do. Moving forward."
Joseph is set to be next through the door, with Boro having spent the last 36 hours putting the finishing touches to their agreement with Hull.
The forward scored eight goals and provided five assists for the Tigers last season and is comfortable playing across the forward line, though it's understood Boro believe his qualities are best suited to playing as a No. 9.