Already ahead 2-0 in the best-of-7 series, the Bruins may be able to field an even more balanced lineup in Game 3 on Monday. Forwards Riley Nash and Tommy Wingels are close to returning from injuries.

Mike Loftus The Patriot Ledger

BOSTON -- Bruce Cassidy is about to encounter a problem, something he considers one of the most difficult aspects of his job.

And he couldn’t feel happier, or more fortunate.

The Bruins’ head coach wasn’t exactly dealing with a makeshift lineup in the first two games of the best-of-7 first round playoff series against the Maple Leafs -- not with everyone on the top two lines, the No. 1 defense pair and the starting goalie all healthy -- but there were some issues below that.

The Bruins beat the Maple Leafs twice despite that, and some of those questions of balance may disappear as soon as Game 3 on Monday night (7:05, NESN, WBZ-FM/98.5) at Air Canada Centre.

Cassidy said on Sunday that Riley Nash, the all-purpose center who missed the last five regular-season games and Games 1-2 of this series with ear and head injuries, “ is looking good, so he will be a guy who could go into the lineup” on Monday. Winger Tommy Wingels, who couldn’t play Game 2 because of the upper body injury sustained on a check that resulted in Leafs’ forward Nazem Kadri being suspended through Game 4, “will be very close, as well.”

In other words, Cassidy is about to have to tell players who have helped the B’s win two playoff games that they’ll have to watch at least the next one.

“We’ve just got to decide what our best fit is for the lineup,” the coach said. “We try to get the best 12 (forwards) in there. Some nights we see certain things falling into place.”

The most likely scenario on Sunday seemed to be that Nash, the Bruins’ No. 3 center when he wasn’t filling in for No. 1 Patrice Bergeron or No. 2 David Krejci, would be ready for Game 3. If so, Noel Acciari would move back to right wing with Tim Schaller and Sean Kuraly, reuniting “a good (fourth) line for us,” Cassidy said.

The B’s would still need a left wing to complete the Nash-David Backes unit. Danton Heinen has played there more than anyone this season, rookie Ryan Donato got a chance there in Game 2, and Wingels has seen time at left wing since the Bruins obtained him from the Blackhawks at the Feb. 26 trade deadline. Veteran Brian Gionta is another option.

“If (Nash and Wingels) are both healthy, and they both come in, who comes out?” Cassidy said. “Those are things internally that we discuss. We’ll have to look at that, and how it affects us if Player A, B or C comes out. You go through all these dominos.”

Nash, who enjoyed a career year (15 goals, 41 points, plus-16) before he was struck on the ear by a Torey Krug shot on March 31, “just sort of sorts everything out for us a little better,” Cassidy said. “He’s going to bring … a little bit of everything. Faceoffs, 200-foot game, matchup guy, kills penalties. He’s gone into the power play position when we’ve had injuries. He can fill in, and move up.”

Cassidy’s not afraid of what might happen if Nash is held out until Game 4 on Thursday, though, because “when he’s not there, I think we’ve handled it well. We just won two games.”

All the same, the B’s would like to have as close to their preferred lineup intact on Monday, when the Leafs -- so far incapable of stopping the Bruins’ Brad Marchand-Patrice Bergeron-David Pastrnak line (5-15--20 over Games 1-2) and power play (5 for 10, 50 percent) from scoring -- will be desperate to get back into the series with a win.

“We know they’re going to have more energy. The fans are going to try to help them out,” said Krejci, who is 2-1--3 between rookie Jake DeBrusk (1-1--2) and Rick Nash (1-0--1) over the first two games.

“Momentum shifts pretty quickly in playoffs, and they’ll obviously be a desperate team. They need to win the next game -- but so do we. We’re going to be desperate, as well. You always want to win the next game.”