JAMES Constable's 11th goal of the season saw Oxford United see off a poor Plymouth Argyle side to claim their first win in six games.
The striker tapped in Damian Batt's 16th-minute cross to put the visitors in front.
They were unquestionably the better side and had chances to win the game more comfortably, but one goal was enough to get past a limited home side, who suffered their first defeat under John Sheridan's stewardship.
Top scorer Tom Craddock returned after missing three games with a groin injury, replacing Deane Smalley in one of two changes to the XI.
Josh Parker was handed his first start for United, coming in for Alfie Potter, who missed out through illness.
Tony Capaldi was also ruled out with a bug, so the visitors could only name six substitutes.
The game took time to get going, but United went in front with the first effort of the afternoon, on 16 minutes.
A neat move saw the ball spread from left to right, with Parker doing well to free Batt. The full back's low cross was perfect for Constable, who had the easy task of tapping in past Jake Cole.
Without creating many chances, United were well in control against a Plymouth side who lacked quality on the ball.
Rigg fired a free-kick straight at Cole, but they had a glorious chance to double the lead on 34 minutes.
Lewis Montrose's ball over the top caught out a flat-footed Argyle back four and United had three forwards versus one defender.
Constable took the ball into the box before electing to square towards Parker and Craddock, but Onismor Bhasera showed fantastic athleticism to get back and divert the ball out for a corner.
It took Plymouth 37 minutes to muster any sort of effort on goal, when Gozie Ugwu flicked a Jason Banton free-kick wide.
Banton, who scored twice against Aldershot last week, tested Luke McCormick four minutes before the break, when the ex-Pilgrims stopper got down low to make the stop.
In stoppage time Constable had another sight of goal following a Montrose through ball, but the striker dragged his left-footed shot wide.
United's only complaint at the break was they were not further in front.
They should have added to the tally eight minutes after the restart, when Durell Berry's back pass went straight to Craddock.
The striker's first touch was heavy and he opted to take the ball around Cole, who pounced on the ball.
A minute later Batt and Craddock combined to play in Constable, whose shot from an acute angle hit the outside of the post.
Plymouth belatedly came to life, exerting some pressure on United's defence for the first time.
The visitors retreated but defended stoutly, with McCormick relatively untested.
Despite enjoying a 20-minute spell, the sum total of Argyle's chances was a shot which Wright headed off the line.
Their best chance came from a scuffed clearance from McCormick, who was well out of his goal. It went straight to Reuben Reid 40 yards out, but instead of trying his luck the striker chose to pass and United scrambled to clear.
The visitors' attacking threat fizzled out almost completely, but with five minutes remaining they were briefly awarded a second goal in bizarre circumstances.
A cross was deflected high into the air by Guy Branston and landed on the roof of the net before Cole tipped it back on to the pitch. It fell to Constable, whose shot trickled in via a defender and to Plymouth's amazement the officials gave a goal.
But after a long discussion between referee Chris Sarginson and his assistant they finally came to their senses and gave a corner.
The break seemed to disrupt Plymouth, who never regained their momentum and United held on for an important and thoroughly deserved win.
Oxford Utd: McCormick, Batt, Raynes, Wright, Davis, Parker, Chapman (Whing 89), Montrose, Rigg (Smalley 62), Constable, Craddock (O'Brien 69).
Unused subs: Crocombe, Heslop, Worley.
Plymouth: Cole, Berry, Branston, Charles, Bhasera, Cowan-Hall, Cox, Hourihane, Banton, Reid, Ugwu (Murray 70).
Unused subs: Chenoweth, Blanchard, Young, Wotton, Richards, Gurrieri.
Referee: Chris Sarginson.
Attendance: 7,189 (311 visitors).