Montemurro won the Continental Cup and a Women's Super League title as Arsenal manager before leaving his role at the start of last season to join Juve, but he departed the Emirates Stadium empty handed courtesy of a lone goal from Vivianne Miedema as Jonas Eidevall's side opened a three-point gap at the top of Group C.
"They're a more complete squad, a more complete team," Montemurro said. "I noticed there's a lot of staff! It's fantastic. It's great that it's growing. I really do wish this great club all the best.
"For us, it was about a little braver in staying high and keeping a high line, not allowing Arsenal to win the ball in certain areas and break. But decisions are decisions on the pitch and I'll never point a finger at a player that tries to be brave or do something."
Juve caused early threat when Leah Williamson failed to clear her lines, allowing the ball to be worked to Barbara Bonansea on the right wing. Her cross was swept towards goal by Arianna Caruso but Manuela Zinsberger was equal to it, with Cristiana Girelli only able to fire wide from the rebound.
Soon after, Stina Blackstenius converted after being played through on goal by Caitlin Foord, but her strike was ruled out for offside.
Juve didn't heed the warnings of that near miss, particularly Blackstenius' burst of pace in behind their back-line, until the Sweden forward helped Arsenal to open the scoring on 16 minutes.
A perfectly weighted pass found Blackstenius in space on the right wing to fire an inch-perfect cross, and Miedema made no mistake in expertly dispatching her half-volley into the roof of the net.
Eidevall's side continued to probe, finding chances plentiful but bearing little fruit in the final third.
The Australian duo of Foord and Steph Catley combined numerous times on the left wing, with the former having her well-struck shot well-saved early in the second half.
Despite enjoying plenty of second-half possession, Montemurro's side failed to break down the resilient Arsenal defence, which has been buoyed by the recent returns to fitness of Williamson and Rafaelle.
"I didn't think I'd play before Christmas so this is great. Four games in 10 days so it's a busy period but I'm not doing anything stupid," Williamson said.
"From our perspective we were in control second half we just had to change what we was doing a little bit we had to be a little bit more defensively resilient but if you look at clear-cut chances we still had it in control but we just had to let them dominate a little bit."
Indicative of Juventus' struggles was Lisa Boattin's desperate strike from 20 yards in stoppage time which flew high and wide, as an out-of-ideas Juve succumbed to Arsenal's professional performance.
Juventus, who won the domestic treble last season, sit third in Group C on five points -- two points behind Lyon who occupy second spot.
"We're not a finished product, especially with the injury situation we have," added Eidevall. "We are constantly changing players. We are improving but we have things to improve on, on and off the ball."