James Constable's double kept Oxford's faint play-off hopes alive as they beat Crewe 2-1.
Oxford's centre forward struck with a goal in each half to take his season's tally to 15 as Crewe lost their eighth away game in a row.
His low 20-yard shot wrong-footed goalkeeper Rhys Taylor to give the U's the lead in the 30th minute and midway through the second half he took a pass from debutant Ryan Burge, muscled his way past a defender, and fired past the keeper again.
United did not have it all their own way though.
Goalkeeper Ryan Clarke turned Shaun Miller's shot away for a corner, and he also made a great one-handed save from Luke Murphy's close-range effort.
And in the closing minutes, Alex's top scorer Clayton Donaldson took the ball around goalkeeper Clarke, but then shot into the side-netting.
Substitute Ajay Leitch-Smith pulled back a consolation goal for Alex deep into stoppage time from the edge of the area, but it came too late.
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