Barnsley plan to bolster their squad with several new players this month after the sale of Mason Holgate to Premier League club Everton.

The 18-year-old defender joined the Toffees yesterday and a Barnsley statement said the fee 'exceeds' the reported figure of £500,000 up front while the Chronicle understands the deal is worth around £2million with add-ons and clauses.

That money – as well as a potential windfall of several millions from the sale of ex-Red John Stones if he leaves Everton – will provide Barnsley with some sizeable funds to spend in the summer transfer window which closes on September 1.

"Mason leaving gives us an injection of finance," chief executive Ben Mansford told the Chronicle.

"To a certain extent, we were waiting for that deal to be concluded so we could move on with bringing players in. We are hoping to bring in three or four players during the next month that we believe will complement the squad we have already assembled and add the competition for places and strength in depth that we need."

Barnsley head coach Lee Johnson, who has been linked once again with Barnet right-back Andy Yiadom and Swindon striker Michael Smith, said: "We have put in a lot of work behind the scenes.  It's difficult to say we have transfers ready to go because they are other clubs' players and a lot still has to happen to get the deals done. But what I will say is that we have plans. We have set wheels in motion and we have the potential for quite a few deals to happen."

Canadian Simeon Jackson is still on trial at Oakwell, where he has been for three weeks. The 28-year-old former Rushden, Gillingham and Norwich striker – who scored three goals in 30 games for Barnsley's League One rivals Coventry City last season – has been reportedly offered a deal by Southend United.

Johnson said: "Simeon is still here and training with up. We haven't actually made him an offer yet but he continues to impress and we'll have to make a decision."

While he is considering adding to his options up front and at full-back, Johnson admits his relatively small squad is unbalanced with at least ten players whose natural position is central midfield.

"We have about 427 midfielders and good ones as well," joked Johnson. He added: "We couldn't turn down Dan Crowley (who signed on loan from Arsenal last month). We didn't really need him but we wanted him. He can play wide and up front too.  It's obvious to me, the fans and the owner that we are overloaded in that area and we will address that.  We have Ryan Williams and Marley Watkins coming back to fitness and, if we sign another winger, then it is starting to look a lot more balanced."

Johnson admits that the Holgate saga – which has rumbled on all summer after the academy graduate rejected an extension of his current deal at the end of last season – has been 'disruptive'. He also said he had been 'told to stay out of it and focus on the team' in the last week following the late withdrawal of Holgate from the squad to face Chesterfield on Saturday due to an imminent deal with Bournemouth whom he eventually turned down in favour of Everton.

Johnson said: "People's heads get turned and sometimes you have to change things at the last minute. Mason is a very good footballer. He's had a good education at a good club.  He's very good on the ball, he believes in himself and he has that football arrogance which is a good thing. He's still got to mature physically and he could fill out and become a centre half or gain a yard of pace which would make him very exciting. That physical maturation will set the ceiling on Mason's career.  He's been a good lad in training and we spoke regularly over the summer."