Tony Mowbray has been one of the less prolific figures in the summer transfer scramble, but it appears the Middlesbrough manager has dealt in quality rather than quantity after his side underlined their promotion credentials with their latest come-from-behind victory.
The win was sealed by second-half goals from Faris Haroun and Malaury Martin, two somewhat low-key free arrivals, who nevertheless showed you needn't necessarily break the bank to bring in players who can prosper.
Haroun enjoyed a dream debut after his introduction at the interval. The attacking midfielder endured a frustrating wait for Fifa clearance for his move from Antwerp-based Beerschot, but made up for lost time by opening his goal account just 23 minutes after coming on to put the hosts ahead. The Belgian international, who appeared to be offside, stabbed the ball home from six yards after a purposeful run and shot from Joe Bennett caused havoc.
Just three minutes later, and only six minutes after entering the fray, Martin, whose one start so far this season came in the Carling Cup, thundered home a stunning 25-yard half-volley.
After Boaz Myhill had kept Middlesbrough at bay early on, the visitors took an undeserved lead from the penalty spot nine minutes before the interval, after Carl Ikeme brought down Chris Burke while gathering the loose ball.
With defenders stationed on the line to ensure he wasn't the last man, the on-loan keeper escaped with a booking, though Adam Rooney exacted maximum punishment from 12 yards with a confident finish low to Ikeme's right, the Irishman's first goal since a summer move from Inverness.
With Haroun immediately to the fore, the hosts were level three minutes into the second-half courtesy of Robson's second goal of the week. The Scot's deflected free-kick found the bottom corner via a post from 25 yards despite the best efforts of Myhill, after Curtis Davies had fouled Marvin Emnes.
It took a desperate block from Davies to prevent Haroun converting a pass from Rhys Williams, but the Belgian was not to be kept off the scoresheet for long, comfortably beating an exposed Myhill as the visitors waited for an offside flag.
Middlesbrough (4-4-2): Ikeme; McMahon, Bates, McManus, Bennett; Robson, Bailey, Williams, Arca (Martin, 67); Emnes, McDonald (Haroun, 46). Substitutes not used Hines, Coyne, Smallwood.
Birmingham City (4-5-1): Myhill; Carr, Davies, Caldwell, Murphy; Burke, Spector (Wood, 72), Fahey, Beausejour, Redmond; Rooney.
Booked: Middlesbrough Robson, Ikeme. Birmingham Caldwell, Burke.
Referee M Brown (E Yorkshire).