United wasted good opportunities against the Saints at the Saint Mary’s stadium and fell behind to Jan Bednarek’s header and James Ward-Prowse’s exquisite free kick before mounting a commendable comeback in the second half to take all three points to Old Trafford.
Substitute Edinson Cavani proved to be the hero of the day for Ole Gunnar Solskjaer’s men as the Uruguayan set up Bruno Fernandes to half the deficit before scoring a brace himself, including a stoppage time header.
The outspoken Keane was unenthused by his former club’s performance at half-time and provided United’s fans with a stark warning in his analysis.
"United have had chances,” Keane told Sky Sports during the half-time analysis.
“It's not good for your health watching Manchester United. They've given away a couple of bad goals, but there's goals here for them.
"The problem is that you just don't know what you are going to get with this United team. We heard Ole and De Gea say before the game that they need consistency, but they are just not backing it up."
United’s win over Ralph Hasenhuttl’s men has taken them to eighth on the table, with a game in hand.
