Backup Lynx point guard Renee Montgomery entered Saturday’s opener against Phoenix on Saturday with just over four minutes left in the first quarter. It is no coincidence that the Mercury — which had made its first eight shots — started to cool off on the offensive end.

On a Lynx team perhaps deeper than any coach Cheryl Reeve has had, much of that depth is at guard, where Montgomery and Jia Perkins back up Lindsay Whalen and Seimone Augustus.

And much of their impact is on defense.

In Saturday’s one-sided victory, Montgomery and Perkins both had five steals. Minnesota turned 15 steals and six other Mercury turnovers ­­into 30 points and enjoyed a 27-10 edge on the fast break.

“When Renee came in, I think as a group we were more disruptive,” Reeve said. “We were getting the ball denials and the pressure we were after. It changed the complexion of the game.”

It might surprise some that Montgomery has found her niche with the Lynx on defense. Acquired in a midseason trade last season, Montgomery — who began her WNBA career in Minnesota — returned with a reputation of wanting to score more than stop the other team from doing so.

But, by the end of the season, the defense that she and Anna Cruz played helped turn the tide in the league finals vs. Indiana.

Not that it was always easy getting Montgomery to embrace that role.

“Two words: Playing time,” Reeve said. “I told her if you’re going to be picked on every possession, because they know you’re going to melt on a screen, it’s going to be hard to keep you out there. She’s a smart player. She made the connection.”

Said Montgomery: “I heard it all the time. And the theme was teams are going to try to pick on me on defense. I mean, I still heard it this year.”

But this year Montgomery has bought in from the beginning. During the offseason, as a free agent, she was courted hard by the New York Liberty. But she chose to come back to Minnesota.

“A lot of people are still confused with my decision,” she said. “In New York, I probably would have been more of a scorer. Bigger role, pretty much bigger, better everything. But I just liked the feel here. I liked how the coaching staff handles things. I loved my teammates. To me it was a no-brainer.”

At 5-7 Montgomery is usually giving up size to her opponent, though her long arms — her teammates call her Go Go Gadget — makes up a bit for that. But even last year, against Phoenix in the Western Conference finals, Reeve didn’t play Montgomery much against the Mercury’s taller lineup.

She had no reservations Saturday, when both Montgomery and Perkins took turns guarding Mercury guard Diana Taurasi. And that will be important Wednesday against a Chicago team that got 45 points from the guard position in a season-opening rout of Connecticut.

Montgomery’s 21½ minutes was tops among Lynx reserves. In that time she scored six points, plus getting those five steals, two assists and playing a lot of defense. In her eighth season, she has found her role on a very good team.

“In 2009 I played pretty good defense as well,” she said, referring to her rookie season with the Lynx. “But this is the peak of my defense right now.”