The Spanish striker drilled home a loose ball in the 41st minute at the Riverside Stadium to fire the Blues in front and send them on their way to victory.
The goal was the forward’s 10th of the season and it proved decisive, as Antonio Conte’s men moved one point clear at the top of the Premier League table.
Speaking to BBC Radio Five Live after the final whistle, Chelsea legend Nevin said: “Not the best game Chelsea have ever played but they got the win they needed.
“You could maybe argue they deserved it during those attacking moments but they lacked slightly in the quality of passing. Middlesbrough could have taken it from them a few times.
“They got the result and that’s all they will care about.”
It marks the first time that Chelsea have moved top of the table since they last won the title in the 2014-15 season.
The Blues ended up 10th in the Premier League last season and without a trophy after a disastrous defence of their title.
The west London side host Tottenham Hotspur in their next Premier League game next weekend.
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