He's certainly glad he didn't.
After a tough opening 45 minutes, Morales scored twice in the second half as the Whitecaps fought back from being a goal down to beat Real Salt Lake 2-1.
"(Substituting Morales) was a conversation we had and me and one of the other coaches disagreed, so I made the decision to keep him on," said Robinson. "Thank God I did."
The influential midfielder missed a great chance early and had a penalty saved in first-half injury time, but rebounded to score from the spot in the 62nd minute after Real went ahead before poking home the winner in the 78th.
"In the second half I felt so much better — more confidence in my play," said Morales. "I had two important goals for the team."
The winner came off a shot from Whitecaps defender Steven Beitashour after substitute Kekuta Manneh made a great run down the left. Morales tore his jersey off in celebration and was mobbed by teammates as Vancouver leapfrogged the Portland Timbers into the final playoff spot in Major League Soccer's Western Conference.
"It's tough to miss a PK, and to bounce back from that the way he did is great," Beitashour said of Morales. "That's why he's our leader. We feed off of it."
Morales tied the score 1-1 midway through the second on penalty after Whitecaps striker Erik Hurtado was brought down in the area. The Chilean designated player stepped up and beat Jeff Attinella to the same side as his earlier miss to breathe life into the crowd at B.C. Place Stadium.
"He's been the leader all season long. He's been great on penalties all season long and nine times out of ten he's going to score," said Whitecaps midfielder Russell Teibert. "That one doesn't go in but he bangs in another one.
"We're down 1-0 and maybe some people are doubting us, but this locker-room believes, our fans believe and this organization believes we can win."
The goal came five minutes after Real defender Nat Borchers scored off a glancing header from a corner kick. Vancouver sagged badly after giving up the first goal in last weekend's 3-0 loss in Portland, but the Whitecaps responded with energy this time.
"I think the reaction was the right one. We got behind each other and we got back into it," said Vancouver goalkeeper David Ousted. "That was one of the reasons we go the win today, the mentality of coming back and supporting each other even though we again go behind even though we were the better team."
The Whitecaps (9-8-13) came into the match two points back of Timbers for the final post-season spot in the West after their Pacific Northwest rivals suffered a 3-2 defeat at Toronto FC earlier in the day. Vancouver now leads Portland by a single point with four games remaining for each club — two home and two away.
"We can take care of our business. We can't take care of what they do," said Robinson. "Today they slipped up a little bit and we took care of business, but there's still lots of points to play for."
Real Salt Lake (13-7-10) needed just a draw to clinch a seventh straight playoff berth, but will instead have to wait at least one more week.
Moments before giving his team the 2-1 advantage, Morales sizzled a shot at Attinella that the 'keeper could only push over the bar, before Real's Sebastian Jaime moved in on Ousted but couldn't get a shot on target after being pressured by a hard-charging Beitashour.
After Vancouver took the lead, Manneh had a chance to ice it but decided against passing to two open teammates and instead tried going it alone against Attinella, who made a good save.
Real pressed forward for a late equalizer, but never really threatened Ousted's goal.
"I'm hot, I'm sweating. It was a great game to watch if you were a neutral," said Robinson. "It was difficult to watch if you were either manager. The game had everything. It had chances, it had penalties, it had wrong decisions, it had right decisions.
"It was good game of football and fortunately we came out with the victory."
The Whitecaps have tumbled down the standings since a good start to the season, winning just three of their last 17 matches coming into Saturday.
Vancouver, which had scored just two goals from open play in its last nine games, came out in its familiar 4-4-2 with a diamond midfield and had more of the ball in the first half but was unable to create much.
The Whitecaps have been criticized for being too cute in trying to score goals, and both Hurtado and Teibert tried efforts from distance early that didn't trouble Attinella.
Morales's two misses bookended a forgettable first half, but Robinson was pleased with how his under-fire players responded.
"The fight and the character that they showed today, not just Pedro but every single player in my group, I'm really pleased for them. It's been tough but it was an important win," said Robinson. "Sometimes you have defining moments in seasons. Maybe this might be our defining moment."
Notes: Morales now has 10 goals on the season, including seven on penalties. ... Attendance was 19,395. ... Vancouver hosts FC Dallas next Saturday, while Real Salt Lake's next MLS game following a mid-week friendly goes Oct. 5 at Chivas USA.