The former Valencia coach is expected to be formally announced as McClaren’s assistant at St James’ Park later this week, but has already spoken about his reasons for accepting a new challenge on Tyneside.
Cathro told BBC Sport: “It’s a forward step to a different type of football. Not stronger or weaker, different.”
The 28-year-old decided earlier this year that he would leave Spain for family reasons at the end of the season, and while he has ambitions to manage in his own right one day, the offer to work as number two to the Magpies’ new head coach was one which proved too good to turn down.
He said: “I wanted a fresh challenge and didn’t want to just sit it out over there and wait for the right manager’s job to come up.
“To come into British football as a manager with no experience of working with English-speaking players is perhaps not advisable anyway, so this makes perfect sense.”
Cathro is likely to be joined at St James’ by former Derby coach Paul Simpson after the Rams revealed on Sunday evening that he is to leave the club on July 1, and the new-look coaching team faces the task of winning over fans who turned on their club as last season unravelled alarmingly.
Owner Mike Ashley reassured supporters that there would be significant investment this summer in an unprecedented television interview on the final day of the campaign, although a concerted search for reinforcements is yet to pay dividends with the first wave of players due back for pre-season training on Wednesday.
Cathro was an amateur footballer for Brechin City, but had never played to a professional level. He had previously been the youth team coach at Dundee United from 2008-2012, before becoming an assistant manager at Portugese team Rio Ave FC and then moving to Valencia in 2014.
The Scottish coach left behind a club which will play in the Champions League qualifying rounds, but he has no regrets about doing so.
He said: “Steve coming in has brought a freshness and enthusiasm to get the club back to where it should be and serve the love that exists for it.
“I’m convinced that it’s a club willing to grow and would be comfortable higher in the league. It’s now ready to do that.
“I’m going to watch Valencia in the Champions League and in La Liga and enjoy them playing in wonderful games in great stadiums.
“But I’ve no fear of missing out because the intention is to go to that level again. If that was with Newcastle, that would be perfect, but if not, I’ll certainly be back working abroad in the next five to 10 years.”