Spurs turned to Mourinho after the north London outfit parted company with Mauricio Pochettino last week following five seasons in charge.
Mourinho returned to Premier League management almost 11 months after the Portuguese head coach was sacked by Manchester United.
The 56-year-old has previously managed Chelsea FC and Manchester United as Spurs become Mourinho’s third Premier League club.
His reputation has been damaged by a largely negative two-and-a-half year spell in charge of Manchester United despite winning the Europa League and the League Cup.
Mourinho made a victorious start to his Tottenham reign on Saturday after Spurs were 3-2 winners against West Ham at the London Stadium.
But former Arsenal midfielder Merson believes Tottenham have made a mistake turning to Mourinho to replace Pochettino at the north London club.
“Jose Mourinho was the best of the best when talking about top managers. But WAS is a very big word when we are talking about the Special One now,” Merson wrote in the Daily Star.
“Football has changed since he was flying high in his glory days with Porto, Chelsea and Inter Milan. Back then you could win games 1-0 and nobody would really care.
“Keep it tight and get the three points was all that mattered. But now there is huge pressure to score goals.
“While you also have the talent around in the Premier League now that makes it even harder to keep clean sheets.
“There is no doubt he is still a very good manager. But I still cannot believe that he is the new Tottenham boss.
“I cannot see the plan behind this, it is simply a quick fix. Spurs have panicked because they are worried they won’t qualify for the Champions League next season.”
Spurs are in ninth position in the Premier League table and nine points adrift of the top four.
Tottenham finished in the top four in their last four seasons under Pochettino, something which the club hadn’t achieved previously.
Spurs lost 2-0 to Liverpool FC in the Champions League final in Madrid last term after Tottenham beat Borussia Dortmund, Manchester City and Ajax in the knockout stages.
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