Tottenham twice came from behind to beat League Two outfit Wycombe Wanderers 4-3 in a thrilling FA Cup fourth-round tie at White Hart Lane. Here are five talking points.

1. Vincent Janssen is left out of the starting line-up but ends up having a big impact

Today’s cup tie, at home against a League Two side, seemed like a big opportunity for Spurs’ misfiring summer signing to get his first goal from open play and gain a useful boost of confidence.

However, the Dutchman was omitted from Mauricio Pochettino’s starting XI, finding himself among the substitutes as Heung-Min Son was chosen to lead the line.

It seemed the manager was easing the pressure on Janssen – the nightmare scenario was another poor performance from the striker, and another blank, against a side lying three divisions below Spurs.

And, as the first half progressed and Wycombe took a 2-0 lead, it seemed a good thing that Janssen was not involved in the embarrassment.

When he was introduced at the interval there was little to lose – and in fact he was able to become a hero, scoring the equaliser and then setting up Son’s late winner. After a bad start, this has to go down as a very good day for the £17million man.

2. Georges-Kevin Nkoudou and Josh Onomah get their first starts for three months – but blow their chances

Both players have struggled for game time this season and, before today, their last starts both came in the League Cup tie at Liverpool in October. They would have been particularly disappointed when they were named on the bench for the FA Cup third-round tie against Aston Villa earlier this month.

However, French winger Nkoduou made a big impact as a substitute that day, setting up Ben Davies’ opening goal and then playing a part in the second, and he was given an opportunity to play from the start on the left flank this afternoon.

Onomah also got the nod against Wycombe, initially taking up a position on the right side of the front four as Pochettino reverted to a 4-2-3-1 system.

The 19-year-old would probably have preferred a central role – and he soon got it as Pochettino ordered him to swap places with Moussa Sissoko in the early stages.

However, Nkoudou was substituted at half-time, having been unable to deliver a consistent end product from the wide areas, and Onomah was somewhat fortunate to escape the same treatment.

There was little improvement though and, after lashing a mis-hit cross into the stands shortly after the break, the teenager was replaced by Dele Alli on the hour-mark.

3. Spurs struggle at the back.

Tottenham’s lack of a cutting edge in the first half was compounded by their problems at the other end.

The centre-back pairing of Kevin Wimmer and 18-year-old Cameron Carter-Vickers had looked very vulnerable in the League Cup defeat at Liverpool in October, and the duo struggled again against Wycombe.

The visitors’ powerful forward Adebayo Akinfenwa bullied both players, even getting a header in on goal directly from goalkeeper Jamal Blackman’s route one free kick in the first half.

Wimmer and Carter-Vickers were particularly culpable when Spurs conceded their second goal, allowing winger Sam Wood to escape between them – and although Carter-Vickers made up the ground, he then slid in from behind to concede a penalty, which was converted by Paul Hayes.

Wimmer ended up being substituted for the second game in a row as Pochettino introduced Mousa Dembele into the midfield on the hour-mark, and Spurs fans will not be too anxious to see the pair reunited.

4. Tottenham battle back again – twice.

Just like at Manchester City last weekend, Spurs found themselves 2-0 down as the hour-mark approached – and, again, they came back to level.

Carter-Vickers’ flicked header found Son and the South Korean’s shot from a narrow angle was deflected past Blackman at his near post.

Pochettino then brought on Dembele and Dele Alli to aid his side’s efforts and, five minutes after Son’s strike, Janssen won a spot-kick, instantly grabbing the ball and firing into the bottom right corner.

But the Lilywhites then suffered a damaging blow when right-back Kieran Trippier limped off, leaving Spurs – who had already made their three substitutions – with 10 men.

It proved important because, with seven minutes of normal time remaining, Wycombe’s Myles Weston was able to burst down into space on Spurs’ right side and hang up a cross for his fellow substitute Garry Thompson, who headed past Michel Vorm.

Spurs still refused to give up though and, in the 88th minute, Alli levelled the scores again. Blackman was at fault as a weak kick fell short of the halfway line, and a simple header forward allowed Alli to run at goal, cut inside and slot home.

It seemed Tottenham had grabbed a replay – but they weren’t even happy with that and went on to win the game at the death.

Deep into the six minutes of injury time, Son played a one-two with Janssen and forced an own goal to book Tottenham’s place in the fifth round.

5. Spurs must improve their squad strength

Tottenham’s first-choice line-up needs little work and will be difficult to improve, but their second-string side still looks too weak to compete in the cup competitions.

Pochettino had to make a half-time change and then two more on the hour-mark to haul his side level with a League Two side at White Hart Lane, and that left him unable to react again when Trippier was injured.

There is unlikely to be any hasty business done in the final three days of this month’s transfer window, but Pochettino will have learned a lot from this match as he considers how he can make Spurs more competitive in all competitions in future.

Follow me on Twitter @BenPearceSpurs and visit my Facebook page at https://www.facebook.com/BenPearceSpurs/