Out of favour at Arsenal, the winger has completed his move to Goodison Park, as the Toffees beat off competition from Southampton and others to land his signature.
“I am thrilled,” Allardyce said. “There was a bit of a chase between a couple of clubs but I think after we set out the ambitions of the club and my ambitions for him he was motivated to come here and refreshed in his mind by the new challenge he can put upon himself.
“He is at a prime age. The prime age of a professional footballer is between 25, 26 and 30, 31. That is when they appear, by all research today, to be at the peak of their careers.
“We have not got too many players in that age bracket in the squad, so he adds one to that. He has a lot of experience and will hopefully provide a lot of excitement for the Everton fans and for us, in terms of getting results, assists and scoring goals.”
You may look at the Blues squad and think a winger isn’t what’s needed.
Allardyce knows his side have been missing pace and, speaking before the Congolese winger's return, he said: “The team has been crying out for what he offers.
“Yannick is blessed with dynamic movements and pace that cause defenders great concern. He probably occupies two players when he’s at his best because he’s such a danger in possession.”
But if Everton were short of a winger, surely they wouldn’t have let Kevin Mirallas leave this month?
Yet, the Belgian’s future was untenable at Goodison Park after a row with first-team coach Duncan Ferguson in November and he had looked set to leave in January regardless of the impact on the Toffees squad.
The 30-year-old had only made five league appearances this season and, when Gylfi Sigurdsson was preferred to him on the wing, it was clear his career at Everton was up.
With Vlašić and Lookman, both aged 20, still unknown quantities, Allardyce is left with two senior wingers.
What’s more, at 30, Lennon’s best days are behind him, and he is out of contract in the summer.
Former Toffee Gerard Deulofeu hasn’t been properly replaced and while there’s a surplus of No.10s, there is space in the squad for a winger.
But how does Walcott compare to Everton’s current crop? We’ve compared him to their current wing options.
With the England international playing just 61 minutes for Arsenal this season, we’ve looked at his league stats from last season, as we have with the fit-again Bolasie.
Vlašić and Lookman have played just 398 and 162 minutes respectively, so they have also been excluded as the youngsters aren’t yet first-team regulars.
And statistically, Walcott outperforms both Bolasie and Lennon – particularly the former Tottenham Hotspur man.
His goals per 90 (0.47), is considerably higher than both Everton wingers, with Bolasie at 0.09, and Lennon failing to score in the league this season. That could just be down to his higher shot accuracy (58 per cent) as well as him taking more shots per 90 (2.9).
Unsurprisingly, that means his xG per 90 is also higher at 0.46. That’s considerably higher than Bolasie (0.11) and Lennon (0.05).
Looking at the trio as a goal threat, Walcott comes out on top while Bolasie is a clear second.
In terms of chances created, it’s the former Crystal Palace man who leads the way with 1.76 per 90, while Walcott comes second at 0.61.
The Arsenal winger has the highest percentage of successful take-ons per 90 (59.42 per cent), while Bolasie actually makes more (3.26). Once again, both outperform Lennon.
It would take the 28-year-old a couple of games to get back into the swing of things but, after he got match fit, if was even 80 per cent of the player he was last season, he’d be an upgrade on Lennon. Furthermore, at £20million, he's not expensive in today's market: Davy Klaassen, who's already out of favour, cost more in the summer.
Walcott’s arrival will give Everton dynamism and pace on both wings, and the Toffees might finally get start to get a return on all the money owner Farhad Moshiri has invested since last summer.