Titus Bramble’s first-half own goal, a deflection from Robin van Persie’s stinging drive, was enough to secure victory over the relegation-haunted hosts, who improved after the break but failed to break down a resolute Reds defence.
The visitors lost Rafael to a groin injury in the first half and his replacement, Jonny Evans, played on after picking up a knock, while David De Gea was temporarily dazed by a clash of heads with Nemanja Vidic.
“I thought it was a battling performance by the players,” Sir Alex said. “We picked up two or three injuries along the way and courage got us through, particularly in the second half.
“In the first half we did well. In the second half you have to give credit to Sunderland – they gave it a real go. They had some fantastic crosses into the box which we had to deal with.
“But our concentration is much better. Early in the season we were losing goals but we’ve got all our defenders back now.”
The win temporarily moved United 18 points ahead of nearest challengers Manchester City, ahead of the Blues’ win over Newcastle.
It means the Reds need just four wins from the remaining eight league games, the next of which is City’s visit on 8 April, to win back a title lost in such heartbreaking fashion last season.
“The players have galvanised themselves,” Sir Alex added. “They’ve shown a