The 28-year-old quickly began repaying the £16million fee paid to Arsenal for his services by helping his new club make a winning start to the Premier League season.
Martinez’s 36th minute penalty save allowed Villa to take three points courtesy of Ezri Konsa’s second half header, in another game against Sheffield United packed with controversy.
June’s meeting between the clubs will forever be remembered for the breakdown of goalline technology and the infamous “ghost goal”.
The first big talking point on Monday night arrived early when John Egan was shown a straight red card after referee Graham Scott ruled he had denied another Villa debutant, Ollie Watkins, a goalscoring opportunity.
Just over 20 minutes later Villa defender Matt Targett was shown only a yellow card after bringing down Chris Basham six-yards out. Both decisions were reviewed and confirmed by VAR. Both were hotly-disputed by Blades boss Chris Wilder and his coaching staff.
Martinez brilliantly kept out John Lundstram’s penalty to deny the 10-men the lead and Villa, laboured in attack for long spells, eventually found a way through when Konsa headed home a corner just past the hour mark.
Villa have spent big during the current transfer window yet on this evidence, it is going to take time for Dean Smith’s team to really hit their stride.
In addition to Martinez and Watkins, Smith also handed a debut to Matty Cash though Villa’s latest signing, winger Bertrand Traore, watched from the directors’ box.
Alongside him in the stands was Mbwana Samatta, with the Tanzanian striker - who has been linked with an exit before the end of the window - one of several notable absentees from Villa’s bench.
There was also no place for Frederic Guilbert, Jota or Henri Lansbury, a stark reminder the club’s focus prior to next month’s deadline will be as much on outgoings as arrivals.
Wilder, meanwhile, handed a first Premier League start to Oliver Burke, following his move from Albion earlier in the month.
Watkins and Cash were quickly into the action as Villa made a bright start, the former finding the latter in space out on the right flank. Cash had time to set himself before crossing deep to the far post where John McGinn, arriving late, was unable to keep his effort on target.
Villa sent plenty of crosses into the Blades box during the opening half without success, Basham making a vital intervention to prevent Douglas Luiz’s effort finding its way through to Grealish.
The first controversial moment arrived on 12 minutes with Egan’s dismissal. Tyrone Mings thumped a long ball forward and as Watkins tried to break reach it, the Blades defender pulled him back, allowing Aaron Ramsdale - who was perhaps a little slow off his line - to come and clear.
Referee Scott wasted no time in showing a straight red card, with VAR Mike Dean then confirming the decision.
Villa looked to strike quickly with the man advantage but found the Blades defence unwilling to buckle, as a series of teasing Hourihane free-kick’s were cleared by hook or crook.
Instead it was impatience which nearly got the better of the hosts when Ezri Konsa over-committed, failed to collect the ball and the Blades broke through Burke.
The Scotland international sent a low cross into the Villa box with Targett upending Basham six yards out.
Much to the fury of Wilder and the rest of the visiting technical area, referee Scott ruled Targett’s challenge to have been accidental and issued only a yellow card.
Moments later their mood darkened further when Martinez dived to his right to brilliantly keep out Lundstram’s spot-kick, pushing the ball round the post.
Villa continued to push and probe early in the second half but their build-up was too often, too slow and on the rare occasions an opening did briefly appear, it was quickly closed by a Blades defender.
Cash saw a shot from the edge of the box, while Watkins directed a Trezeguet cross over the bar.
Judging by how well the visitors had dealt with crosses into the box, you wouldn’t have bet on the breakthrough coming from a corner.
Smith can perhaps claim an inspired substitution, as Hourihane was poised to take the set piece before being substituted for Keinan Davis.
Instead it was Targett who sent in a delivery which Mings flicked on for Konsa to head back across goal and inside the post. It was the defender’s second Premier League goal and he celebrated by sliding in front of the corner flag.
With Davis now playing through the middle, Watkins had switched to the left and the record signing almost created a second for Villa, advancing down the wing before finding Grealish, who curled a shot just wide of the post.
Watkins then sent an effort of his own over the bar, before Grealish pulled a shot wide of the post as the hosts looked for the goal to kill the match off.
Grealish saw another shot deflected over in stoppage time but Villa were not made to pay for their missed chances.
Villa (4-3-3): Martinez, Cash, Konsa, Mings, Targett, McGinn, Luiz, Hourihane (Davis 62), Trezeguet, Watkins, Grealish Subs not used: Elmohamady, Hause, Taylor, Nakamba, El Ghazi, Steer (gk).
Sheff U (3-5-2): Ramsdale, Basham (McBurnie 68), Egan, O’Connell, Baldock, Lundstram, Berge, Fleck (Osborn 63), Stevens, McGoldrick (Ampadu 31), Burke Subs not used: Sharp, Robinson, Norwood, Foderingham (gk).