Stiliyan Petrov is confident Adam Idah and Arne Engels will more than justify their transfer fees. The duo were brought to Glasgow in the summer for a combined £19.5m.
However, some supporters remain unconvinced over the significant spend on the striker and midfielder.
Celtic hero Petrov has no concerns over Idah and Engels, though, as he predicted the pair to improve at Parkhead.
Adam Idah has had limited game time having first been behind Kyogo Furuhashi in the pecking order and then Daizen Maeda emerging as first-choice central striker after his countryman departed for Rennes.
For Petrov, a steady run of significant game time could be all Idah needs to seriously display his quality and potentially nail down the No.9 role.
He said: "I think Adam Idah will come good. In fairness to Idah, he hasn't had a consistent run of games. He hasn't been able to settle in and have 10 to 15 games where he can show what he can do.
"I like Idah. I think he's got certain qualities. He's a typical number nine. He's completely different than Maeda. I believe the team plays differently when Idah is there. The other day I was talking about the difference between Daizen Maeda and Idah.
"What that gives to the team, especially the midfielders, and as a former midfielder myself I loved to play with a number nine who can link up play. Idah can free some space for me because he plays closer to me whereas Maeda is completely different.
"Maeda is quick. He always looks to go in behind. He never really comes close. Nobody is quicker than Maeda. That's why nobody will catch him.
"So, with Idah, you can see him link the play with the likes of Arne Engels and Reo Hatate. They have so many opportunities because they can link up. He's always there. They can find space and it is all about the timing of the run and getting into that space at the right time.
"I think Idah just needs to be patient. He just has to work hard and if he gets a run of games then he can show what he can do.
"Maybe now, with the Scottish Cup semi-final and hopefully the final and the rest of the league games, he will get that opportunity."
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On Engels, Petrov added: "Arne just needs time. It took me a lot of time to adapt and adjust at Celtic but my situation was completely different.
"I had the opportunity to play with very experienced players, good leaders, and players who demanded the ball. The Celtic team is completely different at the moment.
"I had players that I could learn from as Lubo Moravcik, Paul Lambert and Neil Lennon were there. Some players played in that position who could give me a lot of pointers and help me and push me to be competitive.
"At the moment Engels and Hatate are probably the two best midfielders at Celtic and sometimes you need more competition to push them, to encourage them to get better.
"I think Hatate has adapted much better in that position. He is a box-to-box midfielder, he is getting goals and getting in the right areas.
"Engels takes a little bit more time but he definitely has the ability. He has shown that he can play. He is a very intelligent player.
"So, I think he'll be a great addition to this club."
Stiliyan Petrov was promoting Premier Sports’ live and exclusive coverage of St Johnstone v Celtic on Sunday from 2.30 pm on Premier Sports 1. Watch Premier Sports via your TV provider on Sky, Virgin TV, STV Player and Amazon Prime as an add-on subscription, and on the Premier Sports’ streaming platform.”
