Cas were more dominant in the first half than the 18-10 interval scoreline suggested, scoring four tries to two.
Leeds spent much of the opening 40 on the defensive, but took their chances when they came, managing two touchdowns to hang in the game.
The second half was much more event as the teams went try for try and the gap was down to two points going into the final 10 minutes.
Rhinos had the momentum for most of the final period and attacked strongly, but Cas hit them several times on the counter-attack and had just enough credit in the bank to hang on.
Watkins played 59 minutes in his comeback from an anterior cruciate ligament injury suffered last May and, though obviously not match fit, looked very strong.
Early on Tigers looked like a team fresh from a week’s intensive training in the sun and were much sharper than a Leeds side whose timing was off.
That was illustrated best when they created an opportunity on their left, but Jack Walker’s pass went into touch. Leeds, though, got better as the game went on.
With both Tom and Luke Briscoe unavailable due to injury Harry Newman - a specialist centre - got an opportunity on Leeds’ right-wing, but had a tough start up against James Clare who scored a brace of tries in the first half and set up another. The England academy star recovered well though in the second half, scoring a try and looking more solid.
Leeds gave a first appearance to marquee duo Konrad Hurrell and Trent Merrin. Hurrell made some strong carries and lifted the home crowd every time he had the ball. His centre Ash Handley went over twice and if they can get the ball to him, Hurrell is clearly going to be a force in Betfred Super League this year.
Merrin worked hard in defence though the tempo lifted when Stevie Ward and Adam Cuthbertson came on in the first half.
Jacob Trueman kicked well in the first half for Cas and new signing Jordan Rankin, who started alongside him in the halves, caused Rhinos problems with his running game, but Cas lost their way in the second 40.
They were without Greg Eden, Ben Roberts, Jamie Ellis and Oliver Holmes due to injury, along with long-term casualty Luke Gale.
Leeds have Carl Ablett, Dom Crosby and both Briscoes to come in. The first half will keep their feet on the ground, but they can take encouragement from their effort after the break.
Tigers scored in their first attack, from a penalty set. Walker did well to halt a rampaging Mike McMeeken, but Michael Shenton - who had a strong game - went over from Paul McShane’s long pass and Rankin converted from wide out.
That was his only success from six attempts, though none was easy. The visitors got over the line in the next set when Rankin put up a high kick which deceived Handley; McMeeken, Grant Millington and McShane kept the ball alive and Jesse Sene-Lefao forced his way over the whitewash, but was held up.
Two penalties relieved the siege, Merrin was held up and then, after Liam Sutcliffe went close, Watkins touched down at first-receiver from Matt Parcell’s pass. Sutcliffe’s afternoon was cut short when he suffered a foot injury midway through the second half in the build-up to Tigers’ final try.
Cas hit back on 18 minutes when Trueman kicked crossfield and Clare picked Newman’s pocket to touchdown for a well-worked try.
Headingley’s shot clock was used for the first time after 21 minutes when McMeeken spilled the ball from the restart in Merrin and Nathaniel Peteru’s tackle, though the chance came to nothing as Tigers muscled up to shove Brett Ferres into touch.
That scrum almost led to a try when Clare powered down the left-wing, but Brad Singleton brought him down with a stunning ankle tap. However, the reprieve was short-lived. A penalty kept Leeds under pressure and Clare went in for his second try after quick hands by Trueman, Peter Mata’utia and Shenton.
On the other flank Handley was caught out by Mata’utia’s pass to Greg Minikin, but he recovered well to hold the Cas winger up over the line, aided by Parcell and Ferres. In the same set Trueman put another smart kick to the corner, Clare batted it back and Junior Moors touched down.
Leeds’ try soon afterwards was similar. Richie Myler was held up over the line before Lolohea crossed-kicked, Watkins batted the ball back and Adam Cuthbertson got downward pressure, Lolohea adding the extras.
Rhinos had an early chance in the second half, after Newman tackled Clare into touch, but Sutcliffe - playing in the second-row - could not take Lolohea’s short pass close to the line.
However, Rhinos did strike first in the second period, on 45 minutes, Newman reacting quickly to touch down when Lolohea dabbed a short kick in-goal. Lolohea showed some good touches, particularly in the final 40.
At that stage Leeds seemed to be getting on top, but Cas rallied to increase their lead on 51 minutes, in a penalty set. Alex Foster missed the second half of last season through injury, but specialises in scoring against his old club and he maintained that record when he got on the end of Mata’utia’s pass.
You don’t see what happened next very often as Leeds’ restart hit the crossbar and rebounded to Parcell – a tactic devised by Rhinos chief executive Gary Hetherington during his days as Sheffield Eagles’ coach.
A couple of penalties kept Tigers pinned near their own line, Jamie Jones-Buchanan was held up and Leeds eventually made the pressure play when Parcell kept the ball alive and Hurrell’s pass was finished by Handley.
Yes again a try one was was followed by another to the opposition, McShane forcing his way over from acting-half with 19 minutes left.
Whoever plays outside Hurrell will get chance to score this year. With 15 minutes left the big Tongan picked up at acting-half, had a dart and then fired out a pass which sent Handley over. Lolohea broke the long sequence of missed G
Goal kicks with a touchline conversion to cut the gap to two points, but Cas held out under heavy pressure – the home side winning a scrum against the feed at one stage.
The penalty count was nine-six in Rhinos’ favour, five-four to Tigers in the opening period.
Leeds Rhinos: Walker, Newman, Watkins, Hurrell, Handley, Lolohea, Myler, Peteru, Parcell, Singleton, Ferres, L Sutcliffe, Merrin. Subs Cuthbertson, Ward, Dwyer, Jones-Buchanan, Smith, Donaldson, Oledzki.
Castleford Tigers: Mata’utia, Minikin, Foster, Shenton, Clare, Trueman, Rankin, Watts, McShane, Millington, Sene-Lefao, McMeeken, Massey. Subs Milner, Moors, Cook, Clark, Aston, Clarkson, Turner.
Referee: Robert Hicks (Oldham). Attendance: 6,087.