And the tally could soon become eight with Scotland international Kevin Thomson expected to travel to Rockliffe Park for personal talks today after Rangers accepted a £2m offer.
McManus completed a £1.5m switch to the North- East yesterday after turning down Celtic's attempt to extend his stay at Parkhead.
Celtic boss Neil Lennon held face-to-face talks with the defender in an attempt to persuade him to remain in Scotland, but after enjoying a successful loan spell at the Riverside in the second half of last season, McManus expressed a desire to return to Middlesbrough.
The 27-year-old has been one of Strachan's leading targets all summer, and his partnership with fellow centrehalf David Wheater is likely to form the bedrock of Boro's promotion push in the next ten months.
I had to speak to Celtic first because I was still a Celtic player, but I also spoke with Gordon Strachan while I was in La Manga and decided this was the right move for me,
said McManus, who made 16 appearances for Boro last season.
I was lucky to have 12 great years with Celtic, right from leaving school. I was sad to go, but it was the right time for me to move on.
McManus was unable to help Boro secure a play-off place after joining on a temporary basis last January, but having discussed the club's future plans with Strachan this summer, the imposing centrehalf is predicting a bright future on Teesside.
I really enjoyed my time at Middlesbrough last season,
he said. Everyone's been great with me here right from the off. The manager made it clear to me how much he wanted me to come here and in any line of work, you want to go where you are most wanted.
In terms of the decision, I wanted to know what the manager's thoughts and plans were for the future. Obviously, the signings the club has already made are impressive, while it's clear from speaking to him that the manager is ambitious.
All the lads here are ambitious.
This club should be in the Premier League, so promotion is the aim. The Championship is a tough league, but the aim is to go up. It's a big challenge for all of us, but one I am looking forward to.
McManus is the second former Old Firm player to join Middlesbrough this summer, and Strachan is set to complete a hat-trick with the addition of Thomson.
The tough-tackling midfielder is expected to travel to Rockliffe Park this morning after Rangers agreed a £2m fee and gave him permission to head south.
The 25-year-old has been the subject of sustained interest from Strachan for the last month, and while Gers boss Walter Smith had previously been holding out for a sum closer to £3m, a compromise was reached yesterday.
Thomson will now discuss personal terms and undergo a medical, with Strachan hoping to complete the formalities of the move before he takes his senior squad to Ireland for pre-season matches against Athlone Town and Bray Wanderers at the start of next week.
The Boro boss has worked with the Scotland international in the past, as he took him to Coventry City as a teenager, only for Thomson to struggle to settle and quickly return to his homeland with Hibernian.
He left Easter Road for Ibrox in January 2007 and has made more than 100 senior appearances for Rangers in a range of competitions that included the Champions League.
His arrival could spark the exit of Gary O'Neil, with Blackburn boss Sam Allardyce poised to lodge a formal offer for the former Portsmouth midfielder's services.
Strachan will be reluctant to lose his former skipper, but Thomson's arrival could well lead to a parting of the ways.
Source: Northern Echo
Source: Northern Echo