The Gunners were dealt a major blow before this weekend's trip to the King Power Stadium as Kai Havertz was ruled out for the remainder of this season with a torn hamstring.
With Gabriel Jesus also out, Arteta is without a natural centre-forward for the rest of this campaign and is forced to think out of the box for a left-field solution.
Arteta started Leandro Trossard up front against Leicester while Ethan Nwaneri and Raheem Sterling provided the width.
Arsenal were at risk of a frustrating draw as the game was goalless with ten minutes to go. With 20 minutes remaining, Merino replaced an ineffective Sterling and the 28-year-old took Trossard's centre-forward spot while the Belgium international moved wide.
This change worked as Merino struck with two late goals after getting on the end of crosses from Nwaneri and Trossard in Arsenal's 2-0 win, which leaves them four points adrift of table-toppers Liverpool.
Speaking post-match, Arteta gave a reason for selecting Merino as a striker in a comparison with Havertz.
"Today is a day with all the questions that have been raised with the injuries to make a statement, we are here. We really want it," Arteta said.
On the similarities between Havertz and Merino, he said: "Because of the height? No.
"Very different because Mikel (Merino) has never played as a 9 but has got that timing. He can smell the danger. He can anticipate the situation and execute."
Regarding comparisons to former Man Utd star Marouane Fellaini, Arteta added: "I didn't think about it to be fair."
Merino also revealed what Arteta "told" him to do and commented on whether he could remain in this new role in the coming months.
"He (Mikel Arteta) told me to come in as a striker this morning. We were talking about it a little bit with one of the assistants. It is the first time in my career that I've played that position," Merino said.
"He told me to go with my strengths and luckily I could help the team with two goals today."
When asked whether he could start as a striker regularly, he added: "I don't think so to be honest. It is the first time I have scored a brace coming off the bench as a striker.
"I forgot to give my wife something for Valentine's Day so this goes to her. I think she will appreciate this more than a rose and some chocolate.
"Today was a tough game. But I think these games are the ones you need the spirit. Games like today are really good for the squad."
On Ethan Nwaneri, he continued: "He is an amazing player. Every time I do an interview you guys ask me about him.
"We have to keep the foot on the gas and if we keep doing this job then good things will come in the future.
Chelsea's 18-year-old winger Estevao produced an impressive cameo performance off the bench in a 3-0 Premier League victory over Wolves on Saturday, earning praise from manager Enzo Maresca.
Arsenal saw their winning run ended by Sunderland, while Chelsea claimed a convincing victory over Wolves in Saturday's Premier League action.
Mikel Arteta has described Granit Xhaka as "one of the signings of the season" ahead of Arsenal's reunion with their former midfielder when they face Sunderland at the Stadium of Light on Saturday.
Brighton head coach Fabian Hurzeler says his players unanimously believe Danny Welbeck deserves a recall to the England squad, as calls grow for the in-form striker to be included in Thomas Tuchel's selection for this month's World Cup qualifiers.
