Champions League: Jose Mourinho oversees Tottenham's 4-2 comeback win to advance to knockout stages

A bold substitution and a quick-thinking ball boy helped Jose Mourinho turn around his Champions League debut with Tottenham.

It couldn’t have started worse, conceding twice inside 19 minutes to Olympiakos.

A decisive intervention was required by Mourinho in his second match in charge, replacing defensive midfielder Eric Dier with the creative force of the unsettled Christian Eriksen in the 29th minute.

''The most difficult moment of the game for me was not when Olympiakos scored the first or the second goal,” Mourinho said. “The most difficult moment of the game for me was when I made the change in the first half. Hurt the player but hurt myself. Not easy for the player, but not also easy for myself.”

But a call that proved right as a place in the round of 16 was sealed with a 4-2 victory on Tuesday as early goals from Youssef El-Arabi and Borges Semedo were wiped out.

Having been run ragged, Tottenham profited by an Olympiakos blunder in first-half stoppage time when Yassine Meriah completely missed the ball on an attempted clearance, allowing Serge Aurier's cross to reach Dele Alli for a tap-in

Quick action from a ball boy retrieving the ball five minutes into the second half led to Harry Kane leveling the Group B match. Serge Aurier sent a quick throw-in to Lucas Moura, who crossed for Kane to side-foot home.

When it came to celebrating, Mourinho embraced the ball boy.

“I was between 10 and 16 years old, a very good ball boy and the kid is a very good ball boy,” Mourinho said. “He understands the game, reads the game, he's not there just to look to the stands, or to the lights, or to the scarves he's there living the game and playing the game very, very well.

“In the end, I wanted to invite him to the dressing room to celebrate with us, but he disappeared.”

This was not a game when Alli disappeared, unlike so many in the final weeks under Mauricio Pochettino, who was fired last week.

Alli set up the decisive third goal, crossing for Aurier to strike into the net in the 73rd. Kane’s deft header four minutes later completed the fightback, and it came from Eriksen’s free kick — a reminder of the early change from Mourinho.

“We didn't come out with any energy at all really and they got the goal, put us under some pressure, got the second, and it's an uphill battle from there,” Kane said.

“But Dele's done great to get that goal before half time and change the momentum and second half we came out (on the) front foot and got the goals we needed.”

Tottenham is doing its best to make a seamless transition from Pochettino.

There was no on-field photo-call to introduce Mourinho last week nor an introduction at his first home game.

Only the Argentine flag with Pochettino’s photo attached to a stand provided a reminder of the fired manager who took Tottenham to last season’s Champions League final but lost to Liverpool.

Tottenham is ensured of second place in Group B behind Bayern Munich ahead of the final game at the German club, which beat Red Star Belgrade 6-0 on Tuesday.

That means Tottenham can largely focus on the Premier League campaign until the knockout phase begins in February.

Winning the competition for the first time — after losing the June final to Liverpool — might be the only way back in next season.

After four consecutive top-four Premier League finishes under Pochettino, the slide down the standings cost him the manager’s job last week.

The 3-2 victory at West Ham in Mourinho’s first game on Saturday lifted Tottenham to 10th place, nine points from fourth-place Chelsea.

“The levels of the intensity were really, really high at West Ham, and today I decided to play with the same team,” said Mourinho, who only switched Ben Davies with Danny Rose at left back. “Maybe I was wrong. Maybe I should have gone for a couple of changes to give us some more energy.”