The Teessiders' miserable form at the Riverside Stadium proved a key factor in the departure of previous manager Gareth Southgate and the home fans were forced to endure another dismal performance in Strachan's first game in charge in the Championship on Saturday.

Boro struggled throughout against a determined Argyle outfit and fell behind 19 minutes into the second half when Mackie slotted past Brad Jones from 12 yards.

The hosts were given a golden opportunity to level with 10 minutes remaining when Kari Arnason fouled Sean St Ledger in the box, but Adam Johnson drilled the resulting penalty wide.

Victory was no less than Argyle deserved following a spirited display which belied their lowly league position.

Emmanuel Pogatetz and Julio Arca were recalled to the Boro side in the only changes from last weekend's 2-2 draw at Preston, with Joe Bennett and Didier Digard missing out.

Pilgrims boss Paul Sturrock also made two changes to his starting XI, with Yoann Folly and Alan Gow coming in for Jim Paterson and Rory Fallon.

Alan Judge saw an ambitious long-range strike fly narrowly wide for Argyle in the second minute.

Julio Arca and Marvin Emnes both saw shots blocked by Argyle defenders, while at the other end Karl Duguid and Gow both missed the target with attempts from the edge of the area.

Argyle went close again shortly before the half hour when a powerful strike from Judge brought a fine save from Jones.

The Boro goalkeeper was called into action again in the 34th minute to deny Karl Duguid as the visitors began to grow in stature.

Middlesbrough finally managed a meaningful effort of their own four minutes later as Leroy Lita tested Romain Larrieu from 18 yards.

And the hosts had another opportunity on the stroke of half-time when Johnson fired a right-footed shot over the bar.

Strachan looked to increase his side's attacking threat at the break by introducing new loan signing Marcus Bent in place of Marvin Emnes.

Middlesbrough's new boss was forced into another change eight minutes into the second half as Emmanuel Pogatetz left the field on a stretcher following a clash of heads with Shane Lowry.

Jonathan Grounds came on to replace the Austria international and soon after Johnson went close again for Boro with a left-footed shot that whistled wide of Larrieu's near post.

Argyle retained an attacking threat of their own, however, and Mackie saw a well-struck shot beaten away by Jones in the 58th minute.

Six minutes later, Mackie gave the visitors a shock lead as he broke clear before beating Jones with a calm finish.

Bent headed wide from an Arca cross and Gary O'Neil also went close as the Teessiders looked to respond.

But the hosts almost conceded a second with 20 minutes remaining when Arnason headed wide from Gow's corner.

Arnason was then penalised for bringing down St Ledger in the area, but Johnson missed from the spot and Argyle held on for a priceless three points, despite the addition of seven minutes of stoppage time.